The resin casting volume calculator helps you measure exactly how much epoxy resin you need for any mold shape. Buying too little means a ruined pour; buying too much wastes expensive resin. Enter your mold dimensions, shape, and mix ratio to get the exact amounts of Part A and Part B to measure out.
Mold Volume Calculator
Enter mold dimensions and resin mix ratio
Fill mold with water, pour into measuring cup to find volume
How to Use the Resin Casting Volume Calculator
The resin casting volume calculator converts your mold dimensions to the exact resin quantities you need, split by the product's Part A to Part B ratio. Precise measuring prevents the most common resin problems: sticky uncured areas (too little hardener) and excessive heat/warping (too much mixed at once).
Step 1: Measure your mold
For rectangular molds, measure length, width, and depth in inches or centimetres. For cylindrical molds (like silicone cups), measure the inside diameter and height. For complex irregular molds, fill the mold with water, pour into a measuring cup, and enter the volume directly in mL.
Step 2: Check your resin's mix ratio
The mix ratio is printed on your resin kit. Common ratios: 1:1 by volume (equal parts), 2:1 by volume (twice as much Part A as Part B), and 100:45 (often used in casting resins). Some resins specify by weight, not volume — always check the product instructions. This calculator uses volume ratios.
Step 3: Choose an overfill factor
The overfill factor accounts for mixing cup waste, surface tension, and resin that may adhere to your spatula. For thin flat castings, 5% is sufficient. For complex molds or your first time using a product, 15–20% gives you safety margin. Add the extra to a small reserve cup — if the main pour runs short, you can top it up from the reserve before it gels.
Step 4: Use graduated mixing cups
Always measure by volume using calibrated graduated mixing cups, not measuring spoons. Mix slowly for at least 2–3 minutes, scraping sides and bottom, before pouring. Rushing mixing or scraping bubbles in is a leading cause of cloudiness and weak cures. Pour low and slow from one edge of the mold.
Frequently Asked Questions
Is this resin volume calculator free?
Yes, completely free with no signup required. Enter your mold dimensions and get instant resin quantity calculations.
Is my data safe and private?
Yes. All calculations run locally in your browser. No data is sent to any server.
How much resin do I need for a 6x6x1 inch mold?
A 6×6×1 inch rectangular mold has a volume of 36 cubic inches, which equals approximately 590 mL. With a 10% overfill factor, you'd need about 650 mL total. For a 1:1 ratio resin, that's 325 mL Part A + 325 mL Part B. For a 2:1 ratio, it's 430 mL Part A + 215 mL Part B.
What is the difference between 1:1 and 2:1 resin ratios?
The ratio refers to the mix proportions of resin (Part A) to hardener (Part B). A 1:1 ratio means equal volumes or weights. A 2:1 ratio means two parts resin to one part hardener. Always check your specific product label — getting the ratio wrong can result in uncured, sticky resin. Some brands specify by volume, others by weight.
Why do I need an overfill factor?
A 5–15% overfill factor accounts for mixing losses (resin stuck in mixing cups), surface tension, and the fact that resin shrinks very slightly during curing. For large pours, pour slightly more than calculated to ensure the mold stays full after cure. For domed pieces, add 10–15% extra.
Can I mix resin ahead of time?
No. Once Parts A and B are mixed, the curing reaction begins. Most epoxy resins have a 15–45 minute pot life before they become too viscous to pour. Mix only what you can use within the pot life window. For large pours, mix in multiple smaller batches to avoid exothermic heat buildup.