Resin Mixing Ratio Calculator - Resin and Hardener by Weight or Volume

Use the free tool below: your data never leaves your browser — all work happens on your device, and nothing is uploaded to any server.

Getting the resin ratio right, every time

Resin projects fail more often from wrong ratios than from any other cause. Too much hardener and the piece cures brittle, too hot, or with cracks. Too little and it stays soft, tacky, or never fully hardens. The ratio printed on the bottle is not a suggestion: it is the chemistry of that product. This calculator scales any ratio to any batch size, by weight or by volume, so a 2 to 1 resin that you normally mix in small cups can be scaled up to a large pour without mental arithmetic.

The key detail is weight versus volume. Many resins give a ratio by weight, such as 100 to 45, and a different ratio by volume, such as 2 to 1, because resin and hardener have different densities. Mixing a weight ratio by volume, or the reverse, gives the wrong chemistry even when the numbers look right. Check which one your product states, choose it in the calculator, and measure with the right tool: scales for weight, graduated cups for volume.

How to use the calculator

Enter the total batch size you want to mix.
Choose weight or volume, matching exactly what your product label states.
Enter the resin parts and the hardener parts from the label, for example 2 and 1.
Read the two amounts, and measure each one separately.

A worked example

Suppose you need 300 grams of mixed resin at a 2 to 1 ratio by weight. The calculator gives 200 grams of resin and 100 grams of hardener, because the total divides into three parts of 100 grams each. If the same product were mixed by volume at the same numbers, the answer would still be 200 and 100, but in millilitres, and the weights would differ. Never swap the two: a millilitre of hardener does not weigh the same as a millilitre of resin.

Now scale up. A river table pour of 7 litres at 2 to 1 needs about 4.67 litres of resin and 2.33 litres of hardener. Measuring that by eye in a bucket is asking for trouble, so weigh or graduate each part and mix in stages if your container is small. Small, accurate batches beat one large, wrong batch every time.

Safety first, always

Resin work needs good ventilation, nitrile gloves and eye protection. Work in a ventilated space, never in a closed room, and keep resin away from skin: repeated skin contact can cause sensitisation, which means later exposures cause a reaction even from small amounts. Keep the workspace clean, cap bottles promptly, and dispose of mixing cups and gloves as your local rules require. This tool is an educational estimator only, never professional advice, and your product’s datasheet governs every ratio, pour depth and cure time.

Common mistakes

The most common mistake is mixing by the wrong measure, weight instead of volume or the reverse. The second is eyeballing the ratio instead of measuring: a splash more hardener feels harmless, but resin chemistry is unforgiving, and the piece may look fine for a day before it fails. The third is mixing too much at once. Resin cures faster in a large mass because the reaction heats itself, so a big batch can gel in the cup before it is poured.

Another mistake is reusing cups with old resin in them. Uncured residue changes the ratio of the new batch. Use clean cups, clean sticks and clean scales, and write the ratio on a card near the workspace so nobody has to remember it mid-pour.

Who uses a ratio calculator

Jewellery makers use it for small, precise batches where a gram matters. Furniture makers use it for large pours where the cost of a failed batch is high. Beginners use it to build the habit of measuring, which is the single habit that separates successful resin work from sticky failures. Measure twice, mix once, and the chemistry does the rest.

Resin Mixing Ratio Calculator – Resin and Hardener by Weight or Volume