Epoxy Volume Calculator
Calculate the exact amount of resin and hardener needed for a rectangular mold based on dimensions and mix ratio.
About this calculator
This calculator starts from simple geometry — length times width times depth gives the mold's interior volume in cubic inches — then converts that volume to fluid ounces using the standard 0.554 oz-per-cubic-inch factor for resin. The more useful part is the mix-ratio split: rather than just telling you total volume, it divides that total into resin and hardener portions according to the selected ratio (1:1, 2:1, or 3:1), computed as each part's share of the total parts (so 2:1 gives resin two-thirds of the mix, hardener one-third). Both the resin and hardener figures, along with the combined total, get a flat 10% overage added to account for mixing-cup residue and stir-stick loss, since running short mid-pour on a curing resin isn't recoverable.
Gallons are provided alongside ounces for shopping purposes, since resin is commonly sold by the gallon or half-gallon. The critical assumption to get right before trusting these numbers is the mix ratio itself: it must match your specific product's datasheet exactly, not a general assumption about resin type — deep-pour epoxies are commonly 2:1 while tabletop or coating epoxies are commonly 1:1, but there's real variation across brands. Getting the ratio wrong is the single most common way to ruin a pour: too much or too little hardener relative to resin leaves the mixture permanently tacky, cloudy, or soft, since epoxy cure depends on the two components reacting in their specified proportion rather than just being present in some amount.
Inputs
Results
Resin Needed (with 10% overage)
21.95 oz
≈ 6 sticks of butter
Hardener Needed (with 10% overage)
21.95 oz
≈ 6 sticks of butter
How to Use This Calculator
- Enter the mold dimensions: length, width, and depth in inches for rectangular molds.
- Select your resin's mix ratio (1:1, 2:1, or 3:1) from the product label.
- Read the total resin volume needed in ounces with 10% overage, plus the split between resin and hardener parts.
- Use the per-part weights to measure each component separately on a scale before combining.
- Check the gallons output when purchasing resin sold by volume rather than weight.
How the result changes with Mold Length
| Mold Length | Resin Needed (with 10% overage) | Hardener Needed (with 10% overage) |
|---|---|---|
| 6 | 10.97 oz | 10.97 oz |
| 9 | 16.46 oz | 16.46 oz |
| 18 | 32.91 oz | 32.91 oz |
| 30 | 54.85 oz | 54.85 oz |
What each input means
- Mold Length
- Interior length of the mold in inches. Measure the inside dimensions, not the outer mold box.
- Mold Width
- Interior width of the mold in inches.
- Mold Depth / Pour Depth
- Depth of the pour. Most deep-pour epoxies allow 1-2 inches per pour; tabletop epoxies are typically 1/8" to 1/4" per coat.
- Mix Ratio
- The resin-to-hardener ratio specified by your product. Using the wrong ratio will cause improper curing.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersMold Length = 12, Mold Width = 6, Mold Depth / Pour Depth = 1, Mix Ratio = 1 = 4 input(s) provided
- Calculate Resin NeededResin Needed21.95 = 21.95
- Calculate Hardener NeededHardener Needed21.95 = 21.95
- Calculate Total Mixed VolumeTotal Mixed Volume43.88 = 43.88
- Calculate TotalTotal0.343 = 0.343
Engine last updated . Checked against 1 independently-derived test — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
How does the calculator split total resin volume between resin and hardener?
It divides the total mixed volume proportionally by parts: for a 2:1 ratio, resin gets 2 out of 3 total parts and hardener gets 1 out of 3, so resin is exactly two-thirds of the mix and hardener one-third. The same logic applies to 1:1 (even split) and 3:1 (resin gets three-quarters).
Why does the 10% overage get applied to resin, hardener, and the total separately?
The calculator computes resinOzWithOverage and hardenerOzWithOverage each as their own exact figure multiplied by 1.1, rather than splitting an already-inflated total — this keeps the resin-to-hardener ratio intact in the overage amounts too, so you don't end up buying extra of one component but not the other.
Does the mold depth I enter need to match my resin's per-pour depth limit?
The calculator itself just multiplies length × width × depth as pure geometry — it doesn't check your depth against a safe pour limit. Deep-pour epoxies typically allow 1–2 inches per pour while tabletop epoxies are limited to about 1/8" to 1/4" per coat, so if your entered depth exceeds what your specific product allows in one pour, plan multiple pours rather than trusting this single-pour volume as one safe layer.
What's the actual cost of choosing the wrong mix ratio on the calculator versus in real life?
In the calculator, picking the wrong ratio just shifts how the resin and hardener split, in an ounce total, that's still equally computed — the math itself doesn't fail. In real life it's much worse: because cure depends on resin and hardener reacting in their exact specified proportion, mixing at the wrong ratio (say, entering 1:1 for a resin that's actually formulated 2:1) leaves the pour permanently tacky, cloudy, or soft, regardless of how accurately you followed the calculator's ounce totals.
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