Epoxy Mix Ratio Calculator
Weigh or measure a two-part epoxy on-ratio — enter the ratio and total batch, and get exactly how much Part A and Part B to combine.
Weigh out (2:1)
Measure each part accurately and mix thoroughly, scraping the sides — off-ratio or under-mixed epoxy may never fully cure. Follow the ratio on your product’s technical data sheet.
Getting the ratio right
A two-part epoxy only reaches full strength when resin and hardener are combined in the proportion the chemistry needs. That proportion is the mix ratio, and it’s quoted either by weight or by volume — they are not interchangeable, because the two parts rarely weigh the same per millilitre. Weighing on a gram scale is the most repeatable way to hit a ratio like 2:1 or 4:1; measuring by volume with graduated cups works when the data sheet gives a volume ratio.
After you’ve measured the two parts, mixing matters as much as the ratio. Stir thoroughly and scrape the sides and bottom of the cup, because unmixed streaks cure differently from the rest. Then keep an eye on the clock: once combined, the batch is on the pot-life timer, and a large mass runs that timer faster.
Frequently Asked Questions
How do I split a batch to a given ratio?
Each part is the total times its share of the ratio. For a 2:1 mix, Part A is 2/3 of the batch and Part B is 1/3 — so 300 g splits into 200 g resin and 100 g hardener. The calculator does this for any ratio and any batch size, by weight or by volume.
Is a weight ratio the same as a volume ratio?
No — and mixing them up is a common cause of a soft cure. Resin and hardener usually have different densities, so a 2:1 by weight is not the same split as 2:1 by volume. Use whichever basis your product's technical data sheet quotes, and set the calculator to match.
Why does mixing off-ratio matter so much?
Epoxy cures by a chemical reaction between resin and hardener in a fixed proportion. Too much or too little hardener leaves unreacted material, so the bond can stay tacky, cure soft, or end up brittle. Unlike some glues, you can't fix it with 'a bit extra' hardener to speed things up.
What is pot life, and why does batch size affect it?
Pot life is the working time before mixed epoxy gets too thick to use. The reaction is exothermic — it generates heat — and a larger mass traps that heat, which accelerates the reaction and shortens the working time versus the quoted figure (usually measured on a small reference mass). The calculator flags batches over about 100 g for this reason.
How can I keep working time from collapsing on a big mix?
Mix smaller batches, or pour the mixed adhesive into a wide, shallow tray straight after mixing. Spreading it out lets the exotherm heat escape instead of building up in the cup, which buys back much of the working time.
Estimates for planning — not professional engineering advice; follow the adhesive’s technical data sheet for the exact mix ratio, mixing method, and pot life.