Resin Mix Ratio Converter

Epoxy resin and similar two-part systems require precise mixing of resin and hardener in a specific ratio. Getting the ratio wrong can result in a sticky, uncured, or brittle final product.

How mix ratios work: A mix ratio describes the proportion of resin to hardener. For example, a 2:1 ratio by volume means you use 2 parts resin for every 1 part hardener. If you measure 100 ml of resin, you need 50 ml of hardener.

Volume vs weight ratios: Many resin systems specify ratios by weight, not volume, because resin and hardener often have different densities. A 2:1 ratio by weight is NOT the same as 2:1 by volume unless both components have the same density. Always check the manufacturer’s instructions to confirm whether the ratio is by weight or volume.

How far apart are they? Epoxy resin typically runs about 1.10 g/ml and amine hardener about 0.98 g/ml, so the hardener is roughly 11% lighter for the same volume. Convert a ratio with:

• Volume ratio to weight ratio: multiply each side by its own density. A 2:1 by volume becomes (2 × 1.10) : (1 × 0.98), which is 2.24 : 1 by weight.
• Weight ratio to volume ratio: divide each side by its density. A 2:1 by weight becomes (2 / 1.10) : (1 / 0.98), which is 1.78 : 1 by volume.

Mix a 2:1-by-weight system as though it were 2:1 by volume and you end up with about 11% too much hardener. That is enough to leave a soft, slightly tacky surface on a casting that never fully hardens, and no amount of extra cure time fixes it. The densities above are typical, not universal, so put your own product’s figures into the calculator if the technical data sheet gives them.

Common epoxy mix ratios:

Calculating amounts from a ratio: Given a total desired amount and a mix ratio of A:B:

• Resin amount = Total x A / (A + B)
• Hardener amount = Total x B / (A + B)

For example, for 150 ml total at a 2:1 ratio:

• Resin = 150 x 2 / 3 = 100 ml
• Hardener = 150 x 1 / 3 = 50 ml

Important mixing tips:

• Always measure precisely. Even small errors in ratio can prevent proper curing.
• Mix thoroughly for at least 2-3 minutes, scraping the sides and bottom of the container.
• Temperature affects cure time. Warmer temperatures accelerate curing, while cooler temperatures slow it down.
• Working time (pot life) is the time you have to pour and manipulate the mixed resin before it starts to thicken.
• For large pours, mix in smaller batches to avoid overheating (exothermic reaction).
• Use a digital scale for weight-based ratios for the most accurate results.