How much resin does this mold really take?
Mold dimensions to fluid ounces — or type the volume straight in — then the Part A / Part B split at your product's ratio, a waste margin for the cup and the meniscus, and what the pour costs off your kit price. Everything stays in your browser.
The mold
The mix
The numbers here are yours to check. This page does arithmetic on what you type — it cannot see your recipe, your equipment or your batch.
Want it to remember?
In MadeKeeper the kit is inventory by the ounce: every pour consumes its mixed volume, the piece knows its resin cost, and the pigments and glitter ride the same recipe. See for resin artists or poke around the live demo. $19/mo for the whole back office, kept for as long as you stay. The shop stays free for cost a piece and one fair — no product cap. The tax packet, Etsy and Square, and more fairs are the $19.
The pour that cannot come up short
Resin's two disasters — the short pour and the wrong ratio — are both arithmetic. The math below is the same math the calculator runs, stated so you can check it against your own kit's label.
How do I figure a mold's volume?
Length times width times depth in inches, times 0.554 — because one cubic inch is 0.554 fluid ounces, which is geometry rather than opinion. A 4×4 coaster mold at three-quarters deep is about 6.7 ounces of mixed resin. For odd shapes, the honest trick is water: fill the mold, pour it into a measuring cup, dry the mold thoroughly before resin ever touches it.
Is my resin's ratio by volume or by weight?
Whatever the bottle says, and the two are NOT interchangeable. Most craft epoxies mix 1:1 or 2:1 BY VOLUME; some casting resins ratio by weight because their parts have different densities, and using volume cups on a by-weight product under-catalyzes the pour. This page splits whatever total you give it at whatever ratio you enter — reading the label is the one step no calculator can do for you.
Why the waste margin?
Because a short pour cannot be topped up cleanly. Resin left on the cup walls, the mixing stick, and the meniscus you pour just past — it is real volume, commonly a tenth of the batch, and a pour that comes up a quarter-inch shy sets that way forever. Ten percent is the default insurance; deep molds and multiple small molds from one cup both deserve more.
What does a pour actually cost?
The mixed ounces times your kit's price per ounce — a $35 32-ounce kit is about $1.09 an ounce, so the 6.7-ounce coaster mold is an $8 pour with waste. That number is why resin pieces price the way they do, and it is the number that belongs under every price you set.