Epoxy mix ratio calculator

Resin and hardener rarely weigh the same, so a 1:1 ratio by volume is not 1:1 by weight. If your product isn’t listed, enter the specific gravity (weight per ml) of each part from the data sheet. Already poured one part? Choose Part A already measured and the calculator tells you how much of the other to add.

Why volume and weight ratios differ

A mix ratio tells you how much hardener to use for each part of resin. Some products state it by volume (use measuring cups), some by weight (use a scale) and many give both. The two are different because resin and hardener have different densities: epoxy resins are commonly a bit heavier than water, while many hardeners are close to or a little lighter than water.

weight ratio = (A parts × SG of A) : (B parts × SG of B)
volume ratio = (A parts ÷ SG of A) : (B parts ÷ SG of B)   (from a weight ratio)
weight = volume × specific gravity   (1 ml at SG 1.15 = 1.15 g)

With the defaults — 1:1 by volume, Part A at 1.15 and Part B at 0.95 — the weight ratio works out to 100 : 83. So a 16 fl oz batch is 8 fl oz of each part by volume, but about 9.6 oz of Part A and 7.9 oz of Part B on a scale. Weigh them out 1:1 instead and you’d be using about 20% more hardener by volume than intended. That’s close to a real label: TotalBoat lists its TableTop epoxy as 1:1 by volume and 1.2 : 1 by weight.

Worked examples: 1:1 epoxy by weight in grams for a 500 ml art-resin batch, and 2:1 epoxy by weight for a 16 fl oz batch of a deep-pour or laminating resin. If you only need the weight of the whole batch, see how much a gallon of epoxy weighs.

Product presets

Pick a product and the ratio and weights come from the maker’s published figures (checked 2026-09-30) — the label still says “check your TDS”, because makers revise formulas and the data sheet with your batch wins:

• TotalBoat TableTop — 1:1 by volume, 1.2 : 1 by weight. A 500 ml batch is 300 g of Part A and 250 g of Part B.
• EcoPoxy FlowCast — 2:1 by volume, 2.3 : 1 by mass; its data sheet gives specific gravities of 1.122 (A) and 0.978 (B), which work out to 2.29 : 1.
• WEST SYSTEM 105/205 — 5:1 by volume, 5.19 : 1 by weight (WEST’s acceptable range is 4.83 to 6.20 : 1). Most people use WEST’s calibrated pumps; this helps when you weigh instead. WEST publishes no specific gravities for the two parts, so the volume ↔ weight conversion works them out from the 5.19 : 1 ratio at a typical 1.1 g/ml mix — the weights match WEST’s ratio exactly, but the SGs themselves are typical, not published by the maker. TotalBoat TableTop is handled the same way.
• MAS Deep Pour X — 2:1 by volume. MAS doesn’t list a weight ratio or densities on the product page, so the specific-gravity fields stay open for the figures on your data sheet. Leave them blank and the calculator uses 1.15 and 0.97 — typical, not published by the maker, and the same figures the river table calculator uses for it.

Already poured one part?

It happens: you pour a bit too much resin, or you want to use up a partial bottle. Choose Part A already measured (or Part B), say whether you weighed it or used a cup, and enter the amount. The calculator scales the ratio to that amount and gives the other part — by weight and by volume — so the batch stays on ratio. Don’t “round” the other part to make the mix harder or faster; as the measuring tips below explain, that doesn’t work.

Where to find specific gravity

The technical data sheet (TDS) for most epoxies lists the specific gravity or density of each part, and often the mix ratio both ways. Specific gravity is the density relative to water, so an SG of 1.15 means 1.15 g per ml. If the TDS lists a weight ratio, you can enter it directly by switching Label ratio is by to weight — the weights then come straight from the ratio, and the specific gravities are only used for the volume conversion.

Measuring tips

• For small batches — resin art, jewelry, tumblers — weighing is usually more accurate than reading lines on a cup. In US units the calculator shows grams next to ounces for that reason.
• Tare the scale between parts, and pour slowly near the target.
• Don’t “adjust” the ratio for a faster or harder cure. As WEST SYSTEM’s Epoxyworks puts it, changing the amount of hardener doesn’t control cure speed — it leaves a mixture that can never fully cure.
• Mix for the full time on the label, scraping the sides and bottom of the cup.