Epoxy Resin Calculator
Free epoxy resin calculator: enter your surface size and coat depth to get total mixed epoxy and the exact resin and hardener split for your mix ratio.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the formula & steps
How the Epoxy Resin Calculator Works
This calculator does two jobs at once: it finds the total mixed epoxy needed to coat or cast a rectangular surface, then splits that total into the exact resin (Part A) and hardener (Part B) amounts for your kit’s mix ratio. Enter the length, width, coat depth, mix ratio and a waste allowance, and it returns everything in fluid ounces.
The Formula
Epoxy coverage starts with a volume calculation, then a ratio split:
Volume (in³) = length × width × depth Total epoxy (fl oz) = volume ÷ 1.8047 × (1 + waste %) Resin (Part A) = total × A ÷ (A + B) Hardener (Part B) = total × B ÷ (A + B)
There are 1.8047 cubic inches in one US fluid ounce. The mix ratio A:B tells you how to divide the total — for a 1:1 ratio you split it evenly, for 2:1 you take two-thirds resin and one-third hardener.
Worked Example
For a 36 in × 18 in tabletop with a 0.125 in coat, a 1:1 mix ratio, and a 10% waste allowance:
- Volume = 36 × 18 × 0.125 = 81 in³
- Base epoxy = 81 ÷ 1.8047 = ≈ 44.9 fl oz
- With 10% waste = 44.9 × 1.10 = ≈ 49.4 fl oz total
- Resin (A) = 49.4 ÷ 2 = ≈ 24.7 fl oz
- Hardener (B) = 49.4 ÷ 2 = ≈ 24.7 fl oz
Mixing Epoxy the Right Way
- Measure by the stated ratio, not by eye. Off-ratio epoxy is the single most common reason a pour stays soft or tacky.
- Mix thoroughly. Scrape the sides and bottom of the cup for at least 2–3 minutes so every bit of hardener reacts.
- Respect the depth limit. Use a deep-pour formula for casts over 1/4 in to avoid trapped heat.
| Surface | Size (L × W × depth) | Total epoxy (1:1, +10%) | Per part |
|---|---|---|---|
| River coaster | 16 × 16 × 0.25 in | ≈ 39 fl oz | ≈ 19.5 fl oz |
| Bar top | 36 × 18 × 0.125 in | ≈ 49 fl oz | ≈ 24.7 fl oz |
| Deep mold | 24 × 8 × 1 in | ≈ 117 fl oz | ≈ 58.5 fl oz |
Frequently asked questions
How much epoxy do I need to cover a surface?+
Multiply length × width × coat depth in inches, then divide by 1.8047 to get US fluid ounces of mixed epoxy. A 36 x 18 in tabletop with a 1/8 in coat needs about 81 in³, or roughly 45 fl oz before waste allowance.
How do I split epoxy by its mix ratio?+
For a 1:1 ratio, pour equal volumes of resin and hardener. For a 2:1 ratio, the total is divided into three parts: two parts resin (Part A) and one part hardener (Part B). The calculator does this split automatically once you enter the ratio.
What mix ratio does epoxy resin use?+
Common epoxy mix ratios are 1:1 and 2:1 by volume, though some industrial systems use 3:1 or 4:1. Always use the exact ratio printed on your kit. An off-ratio mix may never fully cure and can stay soft or tacky.
How thick can I pour epoxy in one coat?+
Standard tabletop epoxy is poured in coats of about 1/8 in. Deep-pour formulas allow up to 2 in per pour. Pouring a regular epoxy too thick traps heat from the curing reaction and can cause yellowing, bubbles or cracking.
Why add a waste allowance to epoxy?+
Some epoxy always clings to the mixing cup, stir stick and spreader, and self-leveling pours run off the edges. A 5 to 10 percent waste allowance ensures you mix enough to finish the coat without running short mid-pour.