Epoxy mix ratio calculator
Turn a total amount into exact Part A and Part B measurements. Volume and weight ratios are different numbers, so EpoxyPlan uses each product's own published ratio for each.
Volume vs. weight
Resin and hardener usually have different densities, so a ratio by volume is not the same as a ratio by weight. TotalBoat puts it plainly: "Do not use the mix ratio by volume for this method of measuring [by weight] because the densities of the two components are usually not the same."
For example, TotalBoat Fathom is 2:1 by volume but 100:44 by weight. EcoPoxy FlowCast and FlowCast SPR are both 2:1 by volume, yet 2.3:1 and 2.5:1 by weight. Smooth-On EpoxAcast 690 and 692 should only be measured by weight.
Never adjust the ratio
West System: "DO NOT attempt to adjust the epoxy cure time by altering the mix ratio… Most problems related to the curing of the epoxy can be traced to the wrong ratio of resin and hardener."
How the split is calculated
By volume, Part A is the total × A ÷ (A + B). By weight, the total weight is the volume × the mixed density, then split the same way using the weight ratio. Example: 1 gal of Fathom at 2:1 by volume is 85.3 fl oz A + 42.7 fl oz B. At 100:44 by weight and 1.1 g/mL, that's about 2,892 g A + 1,272 g B.