Epoxy Mix Ratio Calculator

Epoxy cures only at the right ratio of resin to hardener, and that ratio comes two ways: by volume or by weight. They are not the same number. A 2 to 1 by volume is not 2 to 1 by weight, because resin and hardener weigh different amounts per milliliter. This works out how much of each part to measure for the batch you want, the way your kit calls it, and gives you the other measure too, so you can weigh a resin that is rated by volume or pour one that is rated by weight.

Volume and weight ratios are not the same number

Your kit prints its ratio one of two ways, by volume or by weight, and they do not match. A 2 to 1 by volume is not a 2 to 1 by weight. Resin is a little heavier per milliliter than hardener, so the moment you switch from measuring cups to a scale, the ratio changes, and you cannot carry one over to the other without accounting for density. Read the label, see which kind it gives, and set that here. Mixing a volume ratio as though it were a weight ratio, or the other way round, is the most common reason a batch never cures.

Why the ratio is exact

This is not like thinning paint, where a splash more or less is fine. Epoxy hardens through a reaction that pairs resin and hardener molecules, so too much of either leaves unreacted material that stays soft or sticky forever. There is no rescuing an off-ratio pour after it has gone off. That is why measuring carefully, and scraping every bit of both parts out of their cups, matters more than any other step.

Weigh it when you can

For small or precise batches, a scale beats graduated cups. Liquids cling to cup walls and the meniscus is hard to read, while a gram is a gram. If your kit gives only a volume ratio but you would rather weigh, this page converts it: enter the volume ratio and your resin and hardener densities, and read the weight figures. Most art and coating epoxies land near 1.1 grams per milliliter for resin and just under 1.0 for hardener, and your data sheet has the exact numbers.

Mix enough, but not too much

Figure the area or the cavity you are filling and mix a little over, because coming up short mid-pour means racing to blend a second batch before the first starts to gel. But do not over-mix either: a big cup of epoxy generates its own heat as it cures, and too large a mass can overheat, smoke or crack. For deep pours, work in shallow lifts and let each cure. Size the batch to the job, with a small margin.

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