How it works
The pour is a box: length × width × depth gives cubic inches. Reduce it by the share of the box that is empty if the wood slabs or inserts fill some of it. Convert to fluid ounces by dividing by 1.8047 (231 cubic inches per gallon, 128 ounces per gallon).
Then split the total between resin and hardener with the manufacturer’s ratio by volume, and add extra for waste. For deep pours, make several layers; most epoxies limit depth per pour to control heat.
Worked example
A 72 in × 6 in river channel poured 1-1/2 in deep with 10% extra at a 1:1 mix:
- Volume = 72 × 6 × 1.5 in × 100% = 648 in³
- With 10% waste = 648 × 1.1 = 712.8 in³
- Fluid ounces = 712.8 ÷ 1.8047 = 395 fl oz (3.09 gal)
- Part A = 395 × 1/2 = 197 fl oz; Part B = 197 fl oz
| Input | Value |
|---|---|
| Length of the pour | 72 in |
| Width of the pour | 6 in |
| Depth of the pour | 1.5 in |
| Share of the box the epoxy fills | 100 % |
| Extra for waste | 10 % |
| Mix ratio by volume (Part A to Part B) | 1 : 1 |
| Result | Value |
|---|---|
| Total epoxy to mix | 395 fl oz |
| Total in gallons | 3.09 gal |
| Part A (resin) | 197 fl oz |
| Part B (hardener) | 197 fl oz |
| Volume with no waste | 648 in³ |
Assumptions and limits
- Rectangular pours only. For a round or irregular shape, estimate the volume separately.
- Mix ratios are volume ratios; weight ratios differ by the density of each part.
- This does not know your product’s maximum pour depth or working time; follow the manufacturer’s data sheet.
Common questions
How much epoxy do I need for a river table?
Multiply the channel length, width, and depth for cubic inches, subtract any space taken by inserts, and divide by 1.8047 for fluid ounces. Add extra for waste.
How many cubic inches are in a gallon of epoxy?
231, the same as any US gallon.
Is my mix ratio by weight or volume?
Check the data sheet. This calculator assumes volume; weight ratios need scale weights.
How deep can I pour epoxy at once?
It depends on the product; deep-pour resins allow several inches, others about an inch or less. Follow the maker’s data sheet.
Sources
- Volume of a rectangular prism; 1 US gallon = 231 in³ = 128 fl oz (NIST Handbook 44 Appendix C).
- Mix ratios come from your epoxy’s data sheet; none is built in beyond the user’s choice.
Updated 2026-09-30