Epoxy Resin Calculator – River Tables, Molds & Coatings
Work out exactly how much epoxy resin to mix for a river table, mold, tabletop, coasters or a flood coat. Get the total in fl oz, gallons or litres, the Part A and Part B amounts, weight, number of pours and kits to buy.
Formula checked 23 Oct 2026Free · no sign-up
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How to use the epoxy resin calculator
Choose what you are making: a river table, a rectangle mold or tabletop, a round piece, or a flood coat over a surface.
Enter the size. For river tables, measure the gap width in three or more places — the calculator averages them.
Enter the depth (or the coat thickness) and how many identical pieces.
Choose the A : B ratio from your kit and, if you know it, the maximum depth per pour.
Optional: enter the kit size and price to see how many kits to buy.
A 48 in long river with widths of 4, 6 and 5 in (average 5 in), poured 1.5 in deep:
Volume = 48 × 5 × 1.5 = 360 in³
360 ÷ 1.80469 = 199.5 US fl oz (1.56 gallons, 5.9 L)
+10% extra = 219.4 fl oz
2 : 1 resin → 146.3 fl oz of Part A and 73.1 fl oz of Part B
Resin needed per square foot
Thickness
Per ft²
Per m²
1/16 in (1.6 mm)
5 fl oz
1.6 L
1/8 in (3.2 mm)
10 fl oz
3.2 L
1/4 in (6.4 mm)
20 fl oz
6.4 L
1/2 in (12.7 mm)
40 fl oz
12.7 L
1 in (25.4 mm)
80 fl oz
25.4 L
Values are rounded (1 in³ = 0.554 fl oz). Add your waste allowance on top.
Tips for a successful pour
Seal the wood first with a thin seal coat. Dry wood absorbs resin and releases air bubbles into the pour.
Seal your mold. Use tuck tape or a melamine/HDPE mold and silicone every seam; a leak overnight is the most common river table disaster.
Measure exactly. Use graduated cups for volume ratios or a scale for weight ratios. Off-ratio resin stays soft or tacky.
Mind the temperature. Most resins want 70–80 °F (21–27 °C). Cold resin is thick and traps bubbles; hot resin cures too fast.
Pour in layers if the depth is more than the label allows. Wait the time stated on the label between layers.
Torch or heat-gun the surface lightly to release bubbles, and cover the piece against dust while it cures.
Frequently asked questions
How do I calculate how much epoxy I need for a river table?
Multiply the length of the river by its average width and the depth. Measure the width in several places because live edges vary, and average them. For a 48 in river averaging 5 in wide and 1.5 in deep: 48 × 5 × 1.5 = 360 in³ = about 200 US fl oz (1.56 gallons). Add about 10% for leaks and what stays in the cup.
How do I convert cubic inches to fluid ounces or gallons?
Divide cubic inches by 1.805 to get US fluid ounces, or by 231 to get US gallons. For metric, multiply length × width × depth in centimetres to get cm³, which equals millilitres; divide by 1,000 for litres.
How much epoxy for a flood coat?
A standard ⅛ inch (3 mm) flood coat needs about 10 US fl oz of mixed resin per square foot, or about 3 litres per square metre. A 2 × 4 ft tabletop (8 ft²) needs about 80 fl oz before waste.
Why can’t I pour all the resin at once?
Epoxy produces heat as it cures. Deep pours trap that heat and can crack, bubble, yellow or even smoke. Each resin has a maximum pour depth on its label — often ⅛–¼ in for coating resin and 1–2 in (or more) for deep-pour casting resin. Enter it to see how many layers you need.
How much extra resin should I mix?
Plan for 5–15% more than the calculated volume. Wood soaks up resin, molds and tape leak a little, and some always stays in the mixing cup. It is far easier than mixing a second small batch mid-pour.
Is the 1:1 or 2:1 ratio by volume or by weight?
Follow your product’s label exactly. Many coating epoxies are 1:1 by volume; many deep-pour resins are 2:1 or 3:1 by volume and give a different ratio by weight. This calculator splits by volume; use our Resin Mixing Ratio Calculator for weight ratios.
How heavy will my river table resin be?
Mixed epoxy weighs about 1.1 g/mL — roughly 9.2 lb per US gallon. A 1.5 gallon pour adds about 14 lb to the table.
How we checked this calculator
We test this tool against worked examples before every release (last check: 23 Oct 2026, version 1.0.0). Results are estimates for planning — confirm critical figures with your supplier or a qualified professional.
