Weed killer concentrate vs ready to use: the buying decision
A concentrate mixed to its own label rate and a ready-to-use trigger bottle put the same amount of ground under spray per litre of liquid. One of them charges you for the water, and the other asks you to measure. This page is the decision about which to buy, and what the number on the front of the box is really counting. How many millilitres go in the tank afterwards is a separate job with its own resource.
By The Weed GuyLast updated
The short version
Buy the concentrate if you have real ground to cover and something to mix it in. It is far cheaper per square metre, because a ready-to-use bottle is mostly water you are paying to have carried to a shop. But it is not the stronger option: mixed to its own label rate a concentrate is often weaker in the tank than the trigger bottle it replaces. And "makes up to 100 litres" is not a promise, it is the label's weakest rate applied to the whole bottle. For a small patio and a handful of weeds, ready to use is the honest answer.
What a bottle actually makes
A yield claim only means something next to the rate that produces it. Here are real bottles with the strength, the label's own rate and the yield in the same row, so you can see which figures agree with each other and which are not published at all.
| Product | Strength | Label rate | What the bottle makes |
|---|---|---|---|
| Roundup Fast Action, ready to use | 7.2 g/L glyphosate | Already mixed, nothing to add | A litre is a litre. The 1 litre pack treats up to 30 sq m |
| Roundup Ultra concentrate, 1 litre | 360 g/L glyphosate | 10ml for annual weeds, 15ml for tough perennials, per litre of water | "Makes up to 100 spray litres" and up to 3,000 sq m, both at the 10ml rate. At 15ml it is nearer 67 litres |
| Roundup Optima+ concentrate, 1 litre | 170 g/L glyphosate | 20ml for annual weeds, 30ml for tough perennials | "Makes up to 50 spray litres" and up to 1,500 sq m. At 30ml, about 33 litres |
| Gallup Home & Garden, 1 litre | 360 g/L glyphosate | 24ml per litre of water, one rate for everything | About 41 litres of spray, treating about 1,670 sq m |
| Weedol Rootkill Plus, 500ml | 120 g/L glyphosate plus pyraflufen-ethyl | 17ml for annual weeds, into 1 litre in a sprayer or 5 litres in a can | "Makes up to 29 litres (for spray use) and 117 litres (for watering can use)". Both figures, one bottle |
| Doff Advanced Concentrated, 1 litre | 90 g/L glyphosate | Not published. The label gives a maximum of 2.4ml per square metre and no water volume | Not published either. Doff states the bottle treats up to 400 sq m |
| Neudorff WeedFree Plus Concentrate, 1020ml | 186.7 g/L pelargonic acid plus maleic hydrazide | 85ml into half a litre of water | About 7 litres of spray from the whole bottle |
Every strength, rate and quoted yield there is the manufacturer's own published figure or its approval record on the HSE garden register. The arithmetic in between is mine, and it is only division, so you can check it. Two things should jump out: the strengths run from 90 to 360 grams a litre under one word, and one of the seven does not tell you how much water to add at all.
"Makes up to 100 litres" is the label at its weakest rate
This is the one I would want to know before buying, and I could not find it written down anywhere. A yield claim is not a measurement of the product. It is the bottle divided by a rate, and the manufacturer gets to pick which rate.
Roundup Ultra's own dilution table is the clearest example, because it prints all of them. Per litre of water in a sprayer it gives 10ml for annual weeds like chickweed and annual meadow grass, 15ml for perennial grasses such as couch, 15ml for tough perennial deep-rooted and broad-leaved weeds, 15ml for areas not intended to bear vegetation, and 20ml to kill a lawn off. The area treated is 30 square metres at every single one of those rates. More product per litre, same ground covered.
So when the 1 litre pack says it makes up to 100 spray litres and treats up to 3,000 square metres, that is the 10ml annual-weed rate multiplied out. Mix it at 15ml for the deep-rooted perennials that actually send people looking for a concentrate, and the same bottle makes about 67 litres and covers about 2,000 square metres. Not a con, and the word "up to" is doing its job honestly. But the headline figure is the easiest weeds you own, and you almost certainly bought it for the hardest.
Optima+ does the same thing at its own strength: 50 spray litres and 1,500 square metres at its 20ml annual rate, roughly 33 litres once you mix it at the 30ml rate for tough perennials. Whatever is on the front of your box, find the rate table on the back and divide the pack by the rate for the weeds you have actually got.
One bottle, two yields, and the reason why
If the point above still feels like nitpicking, there is a 500ml bottle that settles it outright. Weedol Rootkill Plus states, on the same pack: "Makes up to 29 litres (for spray use) and 117 litres (for watering can use)."
Nothing about the weedkiller changes between those two numbers. Its dilution table puts the same measure of product into 1 litre of water if you are using a sprayer, or 5 litres of water if you are using a watering can, and treats the same 20 square metres either way. Pick the watering can and the yield claim roughly quadruples, because you have added four more litres of tap water per dose. The ground you can treat with that bottle has not moved a square metre.
That is the whole thesis of this page printed on one label by the manufacturer. A makes-up-to figure counts water. If you want to compare two bottles honestly, compare what they treat, in square metres, or compare their grams per litre. Never compare their yields.
Concentrate describes the packaging, not the potency
The word on the front of the bottle is a statement about how it is sold, and people read it as a statement about how hard it hits. Two things on the shelf show it is neither a strength claim nor a yield claim.
On strength, take one manufacturer's own range so nothing is being compared unfairly. Roundup Ultra is 360 grams of glyphosate per litre and its label puts annual weeds at 10ml in a litre of water, which works out at about 3.6 grams of glyphosate in your tank. Roundup Fast Action, the ready-to-use trigger bottle nobody rates, is 7.2 grams per litre. That is twice the concentration in the sprayer. And both treat about 30 square metres per litre of liquid, because the label says so in both cases. The concentrate has not been made stronger, it has been left unwatered.
On yield, put Roundup Ultra's "up to 100 spray litres" next to Neudorff WeedFree Plus Concentrate, which is pelargonic acid rather than glyphosate. Its own instruction is to put 85ml of product into half a litre of water. A 1020ml bottle therefore gives you about twelve of those mixes, which is roughly 7 litres of made-up spray in total. One litre against seven, out of two bottles both labelled concentrate, and a fourteen-fold gap in what the word is worth.
The number that survives all of this is grams per litre, next to the label's own rate. That is what the honest verdict on weed killer by product type is built on, and it is the reason a bottle that will not print its strength is a bottle you cannot compare with anything.
Though a bottle refusing to print its strength rarely means the number does not exist. Rootblast Super Strength sells on the word strength and states no grams per litre on its own site or on its retail listings, but its approval is public: MAPP 17836, 360 g/L glyphosate, held by Barclay Chemicals, who also hold Gallup Home & Garden at the same 360 g/L and the same 24ml per litre treating 40 square metres. Two brands, one formulation, one of them telling you what is in it. So the real strength of anything on that shelf is on the HSE garden register under its MAPP number, and the MAPP number has to be printed on the pack. It is the one figure a marketing department cannot edit.
| Product | What is in it | How it is sold, and at what strength |
|---|---|---|
| Roundup Fast Action Pump 'n Go (5 litre) | 7.2 g/L glyphosate, ready to use | Glyphosate ready to use, 7.2 g/L |
| Roundup Ultra Concentrate Weedkiller (500ml) | 360 g/L glyphosate acid, present as 441 g/L potassium salt | Glyphosate concentrate, 360 g/L |
| Neudorff WeedFree Plus (750ml ready to use) | 31.02 g/L pelargonic acid + 4.95 g/L maleic hydrazide | Glyphosate-free ready to use |
| Neudorff WeedFree Plus Concentrate (1,020ml) | 186.7 g/L pelargonic acid and 30 g/L maleic hydrazide | Glyphosate-free concentrate |
| Gallup Biograde Weedkiller, Ready To Use (4 litres) | Glyphosate, listed at 7.2 g/L, ready to use | Pre-mixed, nothing to dilute |
| Gallup Home & Garden Glyphosate Weedkiller (1 litre) | Glyphosate, 360 g/L, as the isopropylamine salt | Glyphosate concentrate, 360 g/L |
| Rootblast Super Strength Concentrate (1 litre) | Glyphosate at 360 g/L, systemic, kills to the root (MAPP 17836) | Glyphosate concentrate, 360 g/L |
| Weedol Pathclear Weedkiller Ready to Use (1 litre) | 3.6 g/L glyphosate and 0.576 g/L diflufenican, ready to use | Ready mixed, plus a residual |
Read it in pairs. Each brand's trigger bottle sits directly above its own concentrate, and the gap between the two lines is not a difference in chemistry or in quality. It is water.
What a sloppy pour actually costs you
The trigger bottle does one thing for you worth naming: it removes any chance of getting the dose wrong. Buying concentrate takes that job back, and the size of the mistake available to you is set by the label rate.
At 10ml per litre of water, pouring 2ml too much is a 20 per cent overdose. At 24ml per litre the same careless 2ml is about 8 per cent, which is neither here nor there. So the tighter the rate, the less forgiving the product, and the tightest rates sit on exactly the bottles advertising the biggest yields. The concentrate marketed as going furthest is the one that punishes a casual pour hardest.
Then there is the bottle that gives you no rate to be accurate against. Doff Advanced Concentrated is 90 g/L glyphosate and publishes a maximum dose of 2.4ml per square metre and a coverage of 400 square metres a litre, but no millilitres-per-litre-of-water figure at all. That is a legitimate way to express a dose and a hopeless one to mix from, because you are standing over a sprayer holding a volume of water, not a measured area of drive.
Two things follow. Measure into something with real graduations rather than the moulded lip on the cap. And when a spray disappoints, under-dosing is a far commoner explanation than the weed being invincible: an over-diluted tank looks and sprays exactly like a correct one, and you find out a fortnight later. Getting the rate onto a real tank volume is its own subject, worked through on the glyphosate concentrate strengths and mixing rates resource, and choosing something to mix it in is on the knapsack sprayer resource.
The concentrate label says things the ready-to-use one does not
There is a straightforward reason a concentrate can carry warnings its own ready-to-use sibling does not: hazard classification is applied to the liquid in the bottle, so it tracks concentration. Dilute the same chemical far enough and it drops below the thresholds that trigger a pictogram. Worth understanding before you decide the concentrate aisle is the serious end of the shop, because the picture is not tidy.
At ready-to-use strength almost the whole shelf is unclassified, and that holds across glyphosate, acetic acid and pelargonic acid alike. Move up to concentrate strength and classifications appear, but not where most people expect. The pelargonic acid concentrates, the ones marketed as the natural alternative, are the ones carrying a Warning signal word, the exclamation-mark pictogram and "causes serious eye irritation": Neudorff WeedFree Plus Concentrate at 186.7 g/L and the two products sharing its formulation. The glyphosate concentrates beside them, Doff Advanced Concentrated and Doff Concentrated Path & Patio, carry no pictogram, no signal word and only a statement about aquatic life.
I am reporting labels, not ranking chemicals, and the two are measuring different things: one is about splashing a strong liquid while you pour, the other about where the spray ends up. The practical upshot for buying is simple. The moment you move from a trigger bottle to a bottle you dilute, you have taken on a handling step the label treats as a different proposition, so eye protection while you pour is not an over-reaction. What happens once the spray has dried is a separate question, answered on whether weed killer is safe for pets and children.
Shelf life runs the opposite way to what people assume
Ask most people which keeps longer, the bottle of concentrate or the sprayer full of mixed weedkiller, and they pick the wrong one. The sealed concentrate is the durable half. The made-up spray is not, and the labels are blunt about it: Gallup's own instruction is to shake the mixture thoroughly and use it immediately after mixing, and manufacturer guidance for consumer and professional concentrates alike is consistent that you mix what you will use in that session rather than keeping a batch.
That turns the buy-the-big-pack instinct into something worth a second thought. A litre advertising up to 100 litres of spray is not offering 100 litres of convenience, it is offering a bottle you will be opening for several seasons, and every one of those sessions is a fresh measuring job. On a 40 square metre drive, which needs somewhere around a litre and a half of made-up spray, that bottle is a very long-term relationship. Nothing wrong with it if you have somewhere safe and locked to keep it in its original labelled container. It is simply not the bargain the per-square-metre figure makes it look.
One timing trap on top, if you are buying volume. Acetic acid amateur weedkillers are on a withdrawal timetable. HSE's amendment notice ends those authorisations on 30 November 2027, permits sale of existing stocks until 31 May 2028, and permits the disposal, storage and use of existing stocks until 31 May 2029. A five litre pack of an acetic acid product bought today therefore has a legal end date attached in a way a glyphosate concentrate does not. Read the active ingredient rather than the shelf label, which goes for the organic and homemade alternatives generally.
The concentrate I would buy
This whole page is the arithmetic for buying concentrate rather than ready-to-use. This is the bottle I would put that arithmetic to work on.
What I’d use
Glyphosate concentrate, 360 g/L
Gallup Home & Garden Glyphosate Weedkiller (1 litre)
The one Gallup a homeowner can legally buy and use: a 1 litre glyphosate concentrate at 360 g/L, approved for home and garden use under MAPP 17672.
It is the same active, the same 360 g/L loading and the same isopropylamine salt as the professional Gallup XL, and its single label rate of 24 ml per litre of water is exactly the rate the professional labels reserve for perennial broad-leaved weeds. The difference between the two bottles is the authorisation printed on them, not the chemistry inside, and this is the side of that line you are allowed to stand on.
- Active ingredient
- Glyphosate, 360 g/L, as the isopropylamine salt
- Formulation
- Soluble concentrate you dilute yourself
- Approval
- MAPP 17672, labelled for use only as a home and garden weedkiller
- Mixing rate
- 24 ml per 1 litre of water, per the label
- Coverage
- 40 sq m per litre of made-up spray, so roughly 1,667 sq m per bottle
- Rainfast
- Rain within 6 hours may reduce effectiveness, per the label
- Size
- 1 litre of concentrate
Watch out for
- No measuring cap in the bottle. Check a cup arrives, or the dose is guesswork.
- One re-treatment a season, and it takes four weeks. Do not go again early.
- Not for lawns. It is non-selective and takes the grass too.
- Resellers dominate the listing, so check the label that arrives is Barclay.
- "Super strength" is keyword stacking. It is 360 g/L, same as professional Gallup XL.
That’s an affiliate link: buy through it and I earn a small commission at no extra cost to you. It doesn’t change what I recommend or what I say is wrong with it. More on how that works in the affiliate disclosure.
No brand pays for a mention here, and nothing on this page is a paid-for opinion. The card above is an affiliate link, so I earn a commission if you buy through it, at no extra cost to you. It buys no product a kinder write-up, which is why the watch-outs sit on the same card as the reasons to buy.
About this resource
I'm The Weed Guy, one bloke who is qualified to use professional weedkiller. Every strength, dilution rate, yield claim and coverage figure on this page is either the manufacturer's own published pack label or the product's entry on the HSE garden register, read in August 2026, and the MAPP numbers are there so you can look any of them up yourself. The sums between those figures are division, and I have shown the working rather than asking you to trust the answer. I have not run these products against each other in a test and I am not going to pretend otherwise.
Where I could not verify something it is not here. There is no price anywhere on this page, because I could not get a UK price I would stand behind at the time of writing, and an invented price is worse than none. The widely-quoted figure of 1,666 square metres per litre for Rootblast is not on any manufacturer source I could find: it is what you get from dividing its real published figures, and it appears on retail listings as though it were a label claim. Roundup Ultra's 500ml pack is not in the table because its label carries the rates but no yield figure, so only the 1 litre pack is quoted.
The mixing itself lives elsewhere. Working a label rate into a 5 or 15 litre tank, the strengths of the named professional concentrates and the certificate rules attached to them are all on the glyphosate concentrate strengths and mixing rates resource, which is what to read once you have decided a concentrate is what you want.
Straight disclosure: nothing here is a paid-for opinion and no brand sponsors this site. Every product named above is named because its label or its register entry carries a figure the argument needed, which is also why the ones that come off worst, the bottle with no published dilution rate and the bottle with no published strength, are named just as plainly as the rest. How I handle commercial relationships across the site is set out on the affiliate disclosure page.
Common questions
Is concentrated weed killer stronger than ready to use?
Usually the opposite, once it is mixed, and you can prove it on one manufacturer's own labels. Roundup Ultra is a 360 g/L concentrate and its label puts annual weeds at 10ml in a litre of water, which is about 3.6 grams of glyphosate in your tank. Roundup Fast Action ready to use is 7.2 g/L in the bottle. That is twice the concentration in the sprayer, in the product everybody calls the weak one. Both treat about 30 square metres per litre of liquid. Concentrate is not the strong option, it is the one that has not had water added for you.
How many litres does 1 litre of weed killer concentrate make?
Anywhere from about 7 litres to about 100, and the word concentrate tells you nothing about which. A litre of Roundup Ultra states it makes up to 100 spray litres. A 1020ml bottle of Neudorff WeedFree Plus Concentrate, mixed at the 85ml into half a litre of water its own instructions give, makes about 7 litres in total. Both sit on the same shelf under the same word. The only figure that decides it is the millilitres-per-litre rate on the bottle in your hand.
What does "makes up to 100 litres" actually mean?
It means the label's weakest rate, applied to the whole bottle, which is rarely the rate you will be using. Roundup Ultra's own dilution table gives 10ml per litre of water for annual weeds like chickweed and annual meadow grass, and 15ml per litre for tough perennial deep-rooted weeds and for areas not intended to bear vegetation. The 100 litre claim is the 10ml figure. Mix it for the perennials most people buy it for and the same bottle makes about 67 litres. The number on the front is a best case, not a plan.
Why does the same bottle claim two different yields?
Because one of them is mostly water, and Weedol Rootkill Plus prints both numbers on the same 500ml pack: "Makes up to 29 litres (for spray use) and 117 litres (for watering can use)". Nothing about the weedkiller changes between those two figures. Its table puts the same dose of product into 1 litre of water for a sprayer or 5 litres for a watering can, treating the same 20 square metres either way. If you ever wanted proof that a makes-up-to figure measures the water rather than the weedkiller, it is printed on that label.
Is weed killer concentrate cheaper than ready to use?
Yes, and by a wide margin per square metre, because you supply the water and the sprayer instead of paying for a trigger bottle full of it. The full price-per-square-metre arithmetic across named products lives on the best weed killer resource rather than here. The thing worth knowing before you buy is that the saving is only real if you spray the ground it covers. A litre making up to 100 litres of spray is a bargain across a big drive and dead money on a small patio.
How do I measure weed killer concentrate accurately?
With something graduated, not the moulded lip on the cap, and the reason is arithmetic. At a 10ml per litre rate, being 2ml out is a 20 per cent dosing error. At 24ml per litre the same 2ml slip is about 8 per cent. So the tighter the rate, the more a casual pour costs you, and the tightest rates sit on the bottles advertising the biggest yields. Measure the concentrate into something with real markings, then scale it to your tank rather than eyeballing a part-filled cap.
Does weed killer concentrate go off, and how long does it keep?
The sealed concentrate keeps far better than the spray you make from it, which catches people out because they assume it runs the other way. Manufacturer mixing guidance for consumer and professional concentrates alike is consistent that you mix only what you will use in that session and spray it out the same day rather than storing a made-up batch. Gallup's own label puts it plainly: use immediately after mixing. So the bottle has the shelf life and the tank does not, and buying a pack that makes far more spray than you will use in a season is not the saving it looks like.
Do I need a licence to buy weed killer concentrate?
Not for an amateur-labelled concentrate, which is what almost everything in a garden centre or a shed is. Gallup Home & Garden spells its status out on the label itself, "FOR USE ONLY AS A HOME AND GARDEN WEEDKILLER", and Roundup Ultra, Optima+, Doff Advanced and Rootblast all sit on the HSE garden register too. The licence question only bites on products labelled for professional use, where the restriction is on the person holding the lance rather than on buying the bottle, and that distinction is covered properly on the glyphosate concentrate strengths resource.
Is a natural or glyphosate-free concentrate the gentler choice?
Not on the hazard labelling, which surprises most people. At concentrate strength the pelargonic acid products, the ones sold as the natural alternative, carry a Warning signal word, the exclamation-mark pictogram and "causes serious eye irritation": Neudorff WeedFree Plus Concentrate and the two products that share its formulation. The glyphosate concentrates beside them, Doff Advanced Concentrated and Doff Concentrated Path & Patio, carry no pictogram, no signal word and only an aquatic statement. That is a report of what the labels say, not a verdict on which chemical is better for you.
Should I buy a big pack of concentrate to save money?
Only if you will use it, and there is a timing trap worth knowing about. Acetic acid amateur weedkillers are on a withdrawal timetable: HSE's amendment notice ends those authorisations on 30 November 2027, allows sale of existing stocks until 31 May 2028 and their use until 31 May 2029. So a large pack of an acetic acid product bought now has a legal end date attached that a glyphosate concentrate does not. Read what the active ingredient actually is before you commit to volume.