Guide . updated 2026-11-14
What rust stain remover really costs per gallon
Short answer: finished rust stain remover costs anywhere from about $2 a gallon if you mix raw oxalic acid yourself, to $10 to $25 a gallon for ready-to-use consumer jugs, to $15 to $25 a gallon for pro concentrates once they are diluted. Pre-measured pods sit in the middle: you pay for the convenience of an exact dose, but you never pay to ship water.
The comparison
These prices come from retailer listings we checked in November 2026. Prices change often, so treat them as a snapshot and check the store before you buy.
| Product | How it is sold | Listed price | Approx. cost per finished gallon |
|---|---|---|---|
| Raw oxalic acid crystals (Florida Laboratories 99.6%) | 5 lb tub, you mix it | $23.99 | About $2 to $4 |
| Iron OUT Outdoor | 128 oz ready to use | $9.99 | About $10 to $18 |
| RustAid Outdoor (Goof Off) | 1 gallon ready to use | $12.99 to $24.78 | About $13 to $25 |
| Evapo-Rust (soak for metal parts) | 1 gallon | $28.99 to $31.49 | About $29 to $31 |
| F9 BARC (pro concrete) | 1 gallon concentrate, up to 3 gallons of spray | $47.50 to $74.65 | About $16 to $25 |
| SpraySticks Backpack Pack | 4 gallon pods, you add water | $49.99 | About $12.50 |
| SpraySticks Pro Pail | 24 gallon pods | $249 | About $10.38 |
What you are actually paying for
Ready-to-use jugs are mostly water. You pay to make it, bottle it, store it and ship it, and acidic cleaners usually travel as regulated hazardous materials, which adds cost all the way down the line. That is why the cheapest jugs live on big box shelves where freight is spread across a whole truck.
Raw crystals strip all of that out, which is why they are so cheap. The tradeoff is that you become the chemist. Oxalic acid powder is an eye and lung irritant, and the mixing advice online is all over the place. Some sources say a quarter cup per gallon, others say a full pound. Too weak and the stain stays. Too strong and you risk etching or bleaching the surface and wasting acid.
Pro concentrates are built for contractors who clean driveways every day and want one product that works fast on heavy irrigation stains. They are priced for that customer.
How to compare fairly
Compare cost per finished gallon at the strength you would actually use, not the sticker price. A concentrate that makes three gallons is not the same as a ready-to-use gallon. Then add what it costs you to get it home: shipping, a trip to the store, or the time it takes to measure powder safely.
Also compare the chemistry. Several popular stain removers contain hydrofluoric acid, which works fast but is one of the more dangerous acids found in household products. Check the safety data sheet before you choose. SpraySticks uses oxalic acid with no hydrofluoric, muriatic or phosphoric acid.
Which one should you buy
If you have one small stain and you are already at the hardware store, a ready-to-use spray is fine. If you are comfortable handling chemicals and you have a lot of concrete to clean, raw oxalic acid is the cheapest route, as long as you wear a respirator and eye protection and measure carefully. If you want the exact dose without handling powder, and you would rather not haul jugs, pre-measured sticks and pods are built for you.
How we will keep this page honest
We will update this table as prices change and add products readers ask about. We list competitor products that cost less than ours, because the point of the page is to help you choose.
Common questions
What is the cheapest rust stain remover per gallon?
Raw oxalic acid crystals are the cheapest, often a few dollars per finished gallon, but you measure and mix them yourself and handle the dust. Big box ready-to-use jugs like Iron OUT Outdoor are the cheapest ready-made option at roughly $10 to $18 per gallon in the listings we checked.
Why do pro concrete rust removers cost so much more?
Contractor products such as F9 BARC are sold as concentrates through pressure washing suppliers, with listings from about $47 to $75 per gallon. A gallon of concentrate makes up to 3 gallons of spray, so the finished cost is lower than the sticker, but still higher than consumer jugs.
Does shipping change the real cost?
Yes. A gallon of ready-to-use liquid weighs over 8 pounds, and acidic cleaners ship as hazardous materials. A dry pod that you mix with your own water ships at a small fraction of that weight.