How to use the epoxy calculator
- Choose what you are filling: a rectangle, a round surface, or a known volume such as a mold you already measured.
- Enter the size in the unit you measured, then the epoxy thickness in mils, inches or millimeters. A mil is one thousandth of an inch.
- Set the mix ratio from the product label (for example 1 to 1 or 2 to 1 by volume) and keep or change the 10% waste. Add a kit size if you want a kit count.
- Read the total volume and the Part A and Part B amounts in gallons, fluid ounces and liters. Use the presets for a garage floor coat or a table pour as starting points.
Formula
Area = length x width, or 3.14159 x (diameter / 2)^2
Volume (cu in) = area in sq in x thickness in inches x number of coats
Volume with waste = volume x (1 + waste percent / 100)
US gallon = 231 cu in, US fluid ounce = 231 / 128 cu in, liter = 1,000 / 16.387064 cu in
Part A = total x A / (A + B), Part B = total x B / (A + B)
Kits = total gallons / kit size, rounded up
One mil is 0.001 inch and one millimeter is 1 / 25.4 inch. A gallon of epoxy spread at 1 mil covers about 1,604 square feet, because 231 cubic inches divided by 0.001 inch is 231,000 square inches.
Worked example: a 10 by 12 foot floor coat at 20 mils
The area is 10 x 12 = 120 sq ft, which is 120 x 144 = 17,280 sq in. At 20 mils (0.02 in) the volume is 17,280 x 0.02 = 345.6 cubic inches, or 1.496 US gallons.
With 10% waste the volume is 345.6 x 1.10 = 380.16 cubic inches, which is 1.646 gallons, 210.7 fluid ounces or 6.23 liters.
At a 1 to 1 mix ratio, Part A and Part B are each half, so you need 105.3 fluid ounces (0.823 gallon) of each.
A table pour of 60 x 24 inches at 2 inches deep with a 2 to 1 ratio works out to 2,880 cubic inches, 13.71 gallons with waste, split into 9.14 gallons of resin and 4.57 gallons of hardener.
Coating thickness versus pour depth
A floor coating is thin, and its thickness is usually quoted in mils on the product data sheet. A river table or casting pour is thick, and the depth is quoted in inches or millimeters. This tool accepts either unit and converts it to inches before it works out the volume, so you never have to convert by hand.
Thick pours behave differently from thin coats. Many products limit the depth you can pour in one layer because the reaction gives off heat, and going over that limit can cause cracking or yellowing. This tool sizes the volume, and the data sheet decides how deep each layer can be.
Mix ratio by volume or by weight
Epoxy systems are made to be mixed at a fixed ratio, and the ratio on the label may be by volume or by weight. This calculator assumes the ratio you enter is by volume. If your product lists a weight ratio, the two parts have different densities, so convert using the data sheet or buy a kit sized for your job.
An inaccurate ratio is one of the main reasons epoxy stays tacky or cures soft. Measure both parts with marked containers, and mix the full amount before pouring.
Why waste matters with resin
Some of every batch stays in the cup, on the stir stick and in the roller. Surfaces are also rarely perfectly flat, and porous surfaces such as concrete soak up the first coat. Ten percent is a starting point, and you can raise it for rough concrete or lower it for a smooth, sealed mold.
Assumptions and limits
- The surface is flat and the epoxy is poured to an even thickness. Sloped floors, textured surfaces and absorbed epoxy are not modeled.
- The mix ratio is by volume. Products specified by weight need a conversion from the data sheet.
- US gallons and fluid ounces are used. An imperial gallon is a different size.
- Waste is an input you control. Coverage from the product label always takes priority over a calculated figure.
- Pot life, cure time, maximum layer depth, temperature limits and ventilation requirements are not checked.
Frequently asked questions
How much epoxy do I need for a table or mold?
Multiply length by width by depth to get the volume, then convert it to gallons. Use the known volume option if you already measured the mold, and add a margin for the mixing cup.
How many square feet does a gallon of epoxy cover?
It depends on thickness. At 1 mil a US gallon covers about 1,604 square feet, so at 20 mils it covers about 80 square feet.
What is a mil?
A mil is one thousandth of an inch, so 20 mils is 0.02 inch. It is the usual unit for coating thickness, not to be confused with a millimeter.
Do I mix epoxy by volume or by weight?
Follow the data sheet for your product. Some systems are specified by volume and others by weight, and using the wrong one can leave the epoxy soft.
Can I use this for resin art or a countertop?
Yes, enter the dimensions and thickness of the pour. A countertop or art piece is a rectangle or circle at the depth you want, plus waste for what clings to the container.