How to work out how much resin I need
Getting your volume right before you mix saves you a second trip to the mixing cup mid-pour, and stops you over-ordering resin that then sits on a shelf. This guide covers how to calculate the volume you need for square, round, and irregular moulds, and how that number changes depending on which Craft Resin product you're using.
Work out the volume
Square or rectangular mould: multiply length x width x height (all in cm). The result in cm³ is the same number in millilitres (1 cm³ = 1 mL), so a mould measuring 20cm x 15cm x 1cm needs 300ml of mixed resin.
Round mould: use radius x radius x 3.14 x height (in cm) for the volume in cm³/mL.
Irregular mould or object: for anything that isn't a clean square, rectangle, or cylinder — a raw-edge charcuterie board, a cast object, a river table with an uneven void — measure by water displacement instead of a formula (see below).
Measuring irregular shapes by water displacement
Line or seal your mould, fill it with water to the level you plan to pour resin to, then pour that water into a measuring jug. Whatever volume of water it took is the volume of resin you need. This works for almost any shape and is more reliable than trying to estimate an irregular void by eye. Pat the mould fully dry before you mix and pour — any leftover water in the mould will cause fisheyes or cloudiness in the cured resin.
Check your depth against the product's max layer
Once you know the total volume, check it against how deep a single pour of that product can go. If your project is deeper than the maximum, you'll need to split the total volume across multiple pours rather than mixing it all at once.
| Product | Mix ratio | Max layer per pour | Recommended batch size |
|---|---|---|---|
| Arts & Crafts | 1:1 by volume | 6mm | Up to 500ml |
| Table Top | 1:1 by volume | 3mm per coat | — |
| Deep Pour | 2:1 by volume (resin:hardener) | 50mm in wide open moulds, 30-40mm in narrow/enclosed moulds | Mix in 2-3kg batches for large projects |
| UV Resin | Single component | — | — |
For example, a 4cm-deep Deep Pour project poured in a narrow mould is within the 30-40mm single-pour limit, but a 6cm-deep pour in the same mould needs to be split into two stages.
Why this matters beyond just avoiding waste
Getting the volume wrong isn't just a cost issue. A batch mixed larger than the recommended size gives you less working time to pour it, not more, because a bigger mass of mixed resin generates heat faster once the resin and hardener start reacting. This is most noticeable with Deep Pour, which cures exothermically: the required room temperature actually drops as your batch gets bigger (1-5kg needs 22-25°C, 5-10kg needs 20-23°C, 10-20kg needs 18-21°C, and anything over 20kg needs below 18°C). So working out your volume accurately up front — rather than mixing extra "just in case" — keeps you within a batch size the product can cure safely.
Once you've calculated your total volume, convert it to parts using the mix ratio for your product (equal parts by volume for Arts & Crafts and Table Top, two parts resin to one part hardener for Deep Pour). It's reasonable to mix a small amount over your calculated figure to cover what's left behind in the mixing cup and on your stir stick — but there's no fixed rule for how much; use your judgement based on the size of your mixing container.
Step-by-step
- Measure your mould or surface. Use length x width x height for square/rectangular shapes, radius x radius x 3.14 x height for round ones, or water displacement for anything irregular.
- Calculate the total volume in mL, remembering 1 cm³ = 1 mL.
- Compare that depth against your product's max layer in the table above — if it's deeper, plan for multiple pours instead of one.
- Convert total volume into mixed parts using your product's ratio (1:1 by volume for Arts & Crafts and Table Top, 2:1 for Deep Pour).
- Mix in batches within the recommended size for your product, especially for Deep Pour, rather than combining everything into one oversized mix.
Related articles
- Mixing Ratio — How to Measure Resin and Hardener Correctly
- How to measure your craft resin
- How to pour your resin mix
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