Epoxy Calculator

Calculate resin and hardener needed for your epoxy project.

This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.

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How to Use the Epoxy Calculator

This calculator estimates the total volume of epoxy you need for a project, then splits that volume into resin and hardener amounts based on your product's mix ratio. Here is how to get an accurate estimate:

  1. Enter your area dimensions. Input the length and width of the surface you are coating in feet. For irregular shapes, measure the bounding rectangle and reduce the depth slightly to compensate, or break the area into rectangles and add multiple passes.
  2. Set your coating depth. This is the key variable. A flood coat on a countertop or table is typically 1/8" (0.125"). A thin seal coat on wood or concrete is 5 to 10 mils (0.005" to 0.010"). Self-leveling floor epoxy usually runs 1/16" to 1/8" per coat. Check your product's technical data sheet for the recommended coverage rate.
  3. Choose your mix ratio. Most casting and countertop epoxies use a 1:1 ratio by volume. Many floor and coating epoxies use 2:1. This is always printed on the product label. Using the wrong ratio will result in an epoxy that does not cure properly.
  4. Set the number of coats. Most projects use two coats: a seal coat and a flood coat. Single-coat applications are common for floors. Thick pours may require multiple flood coats.
  5. Read your results. The calculator shows total gallons, the split between resin and hardener, and a purchase quantity rounded up to the nearest half gallon so you do not run short mid-pour.

Results update instantly as you type. Use the Share button to send your inputs to a supplier, or Copy to paste into a shopping list.

About the Epoxy Calculator

Epoxy is a two-part system: a resin and a hardener that must be combined at a specific ratio before application. Getting the ratio wrong prevents a proper cure. Getting the quantity wrong means either running out mid-pour (which creates a visible seam in a flood coat) or wasting expensive material.

The core formula is straightforward. Volume in cubic inches equals the surface area in square feet multiplied by 144 (square inches per square foot) multiplied by the depth in inches. That cubic volume converts to fluid ounces using the factor 0.554112 (the density ratio of liquid epoxy), and then to gallons by dividing by 128. The mix ratio then splits total volume into resin and hardener portions. Purchase quantity rounds up to the nearest half gallon to ensure you have enough for full coverage.

This calculator handles both thin seal coats measured in mils and thick flood coats measured in fractions of an inch. A mil is one-thousandth of an inch, so a 10 mil seal coat is 0.010 inches. All calculations run entirely in your browser. No data is stored or transmitted.

Frequently Asked Questions

How much epoxy do I need for a 10x12 floor at 1/8" depth?

A 10x12 foot floor at 1/8" (0.125") depth requires approximately 1.30 gallons of epoxy. With a 1:1 mix ratio, that is about 0.65 gallons of resin and 0.65 gallons of hardener. Purchase at least 1.5 gallons (total kit size) to ensure you have enough for complete, even coverage. Many epoxy floor kits are sold in 1.5 or 2 gallon units, which is a good fit for this area.

What is the difference between a seal coat and a flood coat?

A seal coat is a thin first layer (5 to 10 mils, or 0.005" to 0.010") applied to porous surfaces like wood or concrete to seal the surface and prevent air bubbles from escaping into the final coat. It uses very little epoxy. A flood coat is the thick topcoat (typically 1/8" or more) that creates the glossy, durable finish. Most decorative countertop and table projects use both: a seal coat first, then one or two flood coats. Floor coatings may skip the seal coat if the concrete is properly prepared and primed.

Does mix ratio matter if I just add roughly equal amounts?

Yes, mix ratio is critical. Epoxy is a chemical reaction, not a physical mixture. If you add more or less hardener than the formula requires, the excess component will remain unreacted in the cured material. The result is a soft, tacky, or flexible finish that never fully hardens. Always measure by volume using graduated mixing cups, not by weight unless the product specifically gives a weight ratio. Some epoxies use 2:1 by volume but a different ratio by weight. Always follow the specific product's instructions.

How do I account for waste in an epoxy project?

The purchase quantity in this calculator already rounds up to the nearest half gallon as a basic buffer. For most projects, add an additional 10-15% to account for epoxy that sticks to mixing containers, drips over edges, or is lost in foam during mixing. For large flood pours over complex or highly porous surfaces, a 15-20% buffer is safer. It is better to have leftover epoxy than to run short mid-pour, as stopping and restarting a flood coat creates a visible seam that is extremely difficult to fix.