Resin Calculator

Casting and coating are two different sums

If you are filling a mold or a river channel, the number you want is length × width × depth — one pour, one volume. If you are skinning a tabletop, cutting board or set of coasters, depth is not a property of the object, it is a decision you make: how thick you want the coat, times how many coats. Get those mixed up and you can be out by a factor of ten. Pick the matching mode above and the calculator uses the right formula.

One gallon covers 12.8 square feet at 1/8 inch

A US gallon is 128 fluid ounces, and a square foot of surface at 1/8 inch thick holds just under 10 fluid ounces. Coverage halves every time you double the thickness:

Suppliers usually print a slightly lower figure than this table. TotalBoat quotes roughly 12 sq ft per gallon at 1/8 inch, against the 12.8 the arithmetic gives. They are not disagreeing with the maths — they are quoting what you actually get after the stir stick, the cup and the drips take their cut. The table above is the geometry; the allowance below is the difference.

Volume is not the same question as cure depth

This tool tells you how much resin fits in the space. It does not tell you whether that pour will cure safely, and the two are genuinely different problems. Standard tabletop epoxy cooks itself if you pour it deeper than about a quarter inch in one go — the reaction is exothermic, and a thick mass holds its own heat. Deep-pour formulas exist precisely because they cure slower and shed that heat, and even they publish a maximum lift, usually somewhere around two inches. Check your label for that number before trusting a big result here. We have not tried to model it, because every brand's limit is different and the honest answer is on the bottle.

How much extra to mix

Resin left on the stir stick and in the corners of the cup is gone whatever you do, and so is whatever soaks into bare wood on a river table. TotalBoat puts the allowance at 5–10%. Craft Resin says 5–15% and calls 10% a good starting point. This calculator adds 10% by default, and you can switch it off.

Lean to the top of that range on small pours and the bottom on large ones. What stays behind in the cup is roughly a fixed amount, so on a set of coasters it is a large share of the batch and on a river table it is a rounding error. If you are mixing under a pint, 15% is not paranoid.

Other resin calculators

• UV Resin Calculator — for bezels, charms and small molds cured under a lamp, sized in millimetres and priced per piece.
• Glitter Epoxy Calculator — for tumbler coats, where the glitter load changes the amounts.
• Jesmonite Calculator — if you are working in water-based composite instead of epoxy.

Selling the finished pour? Our Etsy Profit Calculator reverses Etsy's 2026 fees so you can set a price that still leaves a margin after the resin costs.