Resin Calculator
Calculate how much resin you need for your mould based on shape and dimensions. Shows Part A and Part B amounts for any mix ratio with cost per piece.
Mould Shape
Dimensions
Mix Ratio
Cost
Total Resin Volume
157ml
0.157L
Mix Ratio: 1:1
Cost per Piece
Based on £25.00/L
£3.93
Resin Tips
- Always measure resin by weight for accuracy
- Mix ratio varies by brand - check instructions
- Account for air bubbles and waste (~10% extra)
- Allow for cure time before demoulding
How Much Resin for My Mould? - The Volume Maths
Volume in millilitres equals the geometry. For a cylinder, it's pi times radius squared times height (a 50mm-diameter, 80mm-tall cylinder mould holds about 157ml). For a cube, it's width times depth times height (40 x 40 x 80 = 128ml). For a sphere, four-thirds pi times radius cubed (50mm diameter sphere holds 65ml). For a dome, pi divided by 3, times radius squared, times height. The calculator does the maths for any of those four shapes plus a custom volume input for irregular moulds.
Once you have the total volume, split it by your mix ratio. A 1:1 epoxy on 100ml total means 50ml Part A and 50ml Part B. A 2:1 ratio means 67ml of A and 33ml of B (the larger number is always the resin, the smaller the hardener, unless your manufacturer says otherwise). The calculator handles 1:1, 2:1, 3:1 and 1:2 in the dropdown. Always read your specific resin's instructions - mixing ratios vary by brand and getting them wrong by even 10% leaves the cure tacky.
Mix Ratios - Why 1:1 vs 2:1 Matters
Most clear casting resin (ArtResin, Pebeo Gedeo, Glass Coat) is 1:1 by volume - equal parts A and B. Some structural epoxies (West System, Smooth-On EpoxyMax) are 2:1 by volume because the hardener is more chemically active. Polyester resin is usually measured by drops or grams of catalyst per 100g of resin and doesn't follow the 1:1 / 2:1 logic at all - the calculator's ratio dropdown is for epoxy, not polyester.
If you mix epoxy at the wrong ratio, the cure suffers. Too much hardener (e.g. you mixed 1:1 a 2:1 resin) leaves the part soft, oily and often white-speckled with unreacted hardener. Too little hardener and the cure is incomplete - the part stays tacky weeks later. Always check the manufacturer's spec sheet, even for 'just clear casting resin' - some brands switched their formula in the last few years and old guides on YouTube are wrong.
Cost Per Piece and Bulk Buying
Resin costs roughly £20-£35 per litre for hobby clear casting resin, £30-£50 for premium UV-resistant brands like ArtResin, and £15-£25 for industrial clear epoxy. The calculator's £25 default sits at the middle of the hobby range. For a 157ml cylinder pour, that's about £3.93 in resin per piece. Add the cost of pigments (£2-£5 per piece), inclusions (£0.50-£20 depending on what you embed), and the mould amortisation if it's a single-use silicone mould.
Bulk buying drops the per-piece cost significantly. A 1L kit at £25 makes about six 157ml pieces; a 5L kit at £100 (£20 per litre) makes 30 pieces with the per-piece cost down to £3.14. If you're selling, the pricing has to cover the labour-intensive sanding, polishing and dome-finishing stages on top of materials - typically 30-60 minutes per finished piece. For pricing handmade pieces against marketplace fees, see the [jewellery pricing calculator](/jewellery-pricing-calculator) and [Etsy fee calculator](/etsy-fee-calculator).
Pour Depth Limits and Why You Can't Just Pour Bigger Moulds
Standard hobby resin has a maximum pour depth of around 1-2cm in a single layer. Pour deeper and the exothermic reaction (resin generates heat as it cures) overheats, yellows the resin, creates bubbles or even cracks the cured piece. For a 5cm-deep mould, you have to pour in 2-3 layers, waiting 4-12 hours between layers for the previous layer to gel. The calculator gives you total volume; planning the layer schedule is on you.
If you need a single deep pour (a 10cm river table, a thick paperweight), switch to deep-pour resin (also called 'casting resin' as opposed to 'coating resin'). Deep-pour resins like Liquid Glass Deep Pour, Stone Coat Countertops Super Cast and Smooth-On Crystal Clear have slower cures (24-72 hours) that release heat gradually and let you pour 5-10cm in one go. They cost more per litre (£35-£60) but eliminate layer lines and save days of work. Match the resin to the depth before you order.
Frequently Asked Questions
How accurate is the volume calculation?
The volume maths is exact for the geometric shapes (cylinder, cube, sphere, dome). Real moulds often deviate slightly - silicone moulds flex when filled, air pockets form, and the surface tension of resin means it usually pours about 1-2% short of the geometric volume. Mix 5% more than the calculator says for any project where running out mid-pour would ruin the piece.
Should I measure by weight or volume?
Volume is the standard for epoxy resin manufacturers' instructions. Weight (grams) is more precise but only works if your resin spec lists density - most brands give the ratio in volume. For very small batches under 30ml, weight on a 0.1g scale is more accurate than measuring cups. For batches over 100ml, volume in graduated mixing cups is faster and accurate enough.
What's the difference between Part A and Part B?
Part A is the resin (the larger of the two for non-1:1 ratios). Part B is the hardener (the smaller). They're chemically inert until mixed; once combined, they cure within hours via an exothermic reaction. Always store them separately, never mix until you're ready to pour, and never add more hardener 'to speed it up' - that just creates a hot, brittle, yellowed piece. If your resin is curing too slowly, raise the room temperature to 22-25°C, which speeds the reaction without changing the chemistry.
Can I save leftover mixed resin?
No. Once Part A and Part B are mixed, the chemistry is running and the resin will cure in the cup whether you use it or not. Leftover mixed resin is a hot, sometimes smoking, definitely-going-in-the-bin disaster. Plan portions tightly using this calculator and pour any small leftover into a silicone offcut mould as a 'bonus piece' rather than letting it cure in the mixing cup.
Does the calculator work for UV resin?
Yes for the volume calculation, no for the mix ratio. UV resin cures via UV light alone and is not mixed with a hardener - it's a single-part product. Set the mix ratio to anything (it's ignored) and use only the total volume figure. UV resin is best for shallow, small pieces (jewellery, small charms) because UV light only penetrates 3-5mm; for anything larger, switch to two-part epoxy.
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