Resin Calculator: How Much Resin Do I Need?

Enter your mold or surface size and this calculator tells you how much resin to mix in total, how much Part A and Part B that is for your label’s ratio, and how many layers to pour it in. It works for round and rectangular molds, coating a flat surface, and odd shapes you measure with water. It measures by volume, in US fluid ounces and milliliters.

1. What are you filling?
2. Units

Measure the inside of the mold. Fractions work too: 1/4 or 3 1/2.

Fill the mold with water, pour it into a measuring cup and enter the amount. Then dry the mold completely before you pour resin: water left behind can turn resin cloudy.

3. Your resin
Use the numbers on your label. The defaults are our usual starting points, not your resin’s limits.
Extra options

Enter your sizes above to see how much to mix.

Whatever the result says, wear nitrile gloves and eye protection when you measure and mix, and work with real airflow. More in resin PPE for beginners.

How to use the calculator

  1. Pick what you're filling. Round for coasters and dishes, square or rectangle for trays and box molds, coating for artwork or a tabletop, and odd shape for anything else.
  2. Measure the inside of the mold, not the outside, and only as deep as you plan to fill it. Fractions like 1/4 or 3 1/2 work.
  3. Choose your resin and its ratio. Use the mixing ratio printed on your label. If it isn't 1:1, 2:1 or 3:1, choose "Other" and type both numbers.
  4. Check the maximum pour depth on your label and put it in the layer box. The calculator then tells you whether the piece needs more than one pour.

Under Extra options you can change how much extra it adds (10% to start) and take off space for wood or other things sitting in the mold, which matters a lot for wood-and-resin pieces.

How the calculator works it out

It works out the volume of the space you're filling, then turns it into fluid ounces and milliliters:

  • Round: 3.1416 × radius × radius × depth
  • Square or rectangle: length × width × depth
  • Coating: length × width × coat thickness

One cubic inch is about 16.39 ml, and one US fluid ounce is about 29.57 ml (NIST). Then it multiplies by the number of pieces, adds your extra, and splits the total by your ratio.

A worked example. Four round coasters, 4 inches across and 1/4 inch deep: each one holds about 1.7 fl oz (51 ml). Four of them come to about 7 fl oz, and with 10% extra that's about 7.7 fl oz (227 ml), or 3.8 fl oz each of Part A and Part B for a 1:1 epoxy. That's why I plan on about 8 oz for a set of four. The coaster guide has a table for other sizes.

Why the calculator adds extra

Some resin always stays on the cup walls and the stir stick, and running short halfway through a pour is worse than having a little left over. Mixing a little more rather than a little less is standard advice. Keep a spare small mold or two nearby for the leftovers. If you're coating a surface and letting resin run over the edges, raise the extra.

When a pour needs layers

Epoxy warms up as it cures, and a pour that's too thick can overheat. That's why resin labels give a maximum pour depth, and why thin layers are the safe default. The calculator's starting points are about 1/4 inch per layer for coating epoxy and about 1/16 inch (2 mm) per layer for UV resin. Deep-pour epoxy varies too much between brands to guess, so that box starts empty. Always go by your own label.

Some labels also cap how much you mix at once, not just how deep. Let's Resin, for example, says not to pour more than 200 ml at a time into a casting mold. If one layer comes out bigger than your label allows, split it into smaller batches. Not sure which kind of resin you have? See casting vs coating resin.

Odd-shaped molds: use water

For hearts, spheres, letters or anything with curves, the most reliable measure is water. Fill the mold with water, pour it into a measuring cup, and enter that amount under "Odd shape". You won't catch every drop, so keep the extra on. Then dry the mold completely before you pour: water left in the mold can make resin bubble or turn cloudy.

Measuring by volume, not weight

Most craft epoxy ratios are by volume, so the calculator gives volumes to measure in marked cups. If you'd rather use a scale, use the weight ratio your maker publishes. It isn't the same as the volume ratio, because resin and hardener have different densities. ArtResin, for example, is 1:1 by volume but 100:84 by weight. Step-by-step mixing is in how to mix epoxy resin.

Buying resin? Size up

Once you know how much one project takes, check it against the kit size before you buy. In my Let's Resin kit review I explain why I'd buy a bigger kit than you think you need. For trays and bigger pieces, see the serving tray guide.

Resin calculator FAQ

How much resin do I need for coasters?

For four round coasters 4 inches across and 1/4 inch deep, mix about 8 fl oz (about 230 ml) in total. Each coaster holds about 1.7 fl oz (51 ml), and about 10% extra covers what stays in the cup. For a 1:1 epoxy that's about 4 fl oz each of Part A and Part B.

How much resin do I need per square foot?

At 1/8 inch thick, one square foot takes about 10 fl oz (295 ml) of mixed resin. At 1/4 inch it takes about 20 fl oz (590 ml). Add extra if you let the resin run over the edges, and check your label for how thick one coat can be.

How do I work out resin for an odd-shaped mold?

Fill the mold with water, pour the water into a measuring cup and use that amount, plus a little extra. Dry the mold completely before you pour, because water left in the mold can make resin bubble or turn cloudy.

Can I measure resin by weight instead?

Only if your maker publishes a weight ratio, and then use that ratio, not the volume one. Resin and hardener have different densities, so the two ratios differ. ArtResin, for example, is 1:1 by volume but 100:84 by weight. This calculator gives volumes.

Does the calculator work for UV resin?

Yes. Choose UV resin as the type. UV resin is one part, so there is no ratio to split. The calculator starts at about 1/16 inch (2 mm) per layer and tells you how many thin layers to cure. Check your own label for its layer limit.

How do I know how many layers to pour?

Divide the depth you want by the maximum pour depth on your label and round up. A 1/2-inch piece in a resin rated for 1/4 inch per layer needs two pours. The calculator does this for you once you enter your label's number.

Sources

Checked 8 October 2026.