Epoxy Volume Calculator: Resin & Hardener Mix

This epoxy volume calculator works out the total volume of mixed epoxy you need for a rectangular or cylindrical pour, and it also splits that total into the exact resin and hardener parts based on your mix ratio. You enter the dimensions of your project (length, width, and depth, or diameter and depth), the mix ratio, and a waste allowance percentage, and it returns the total volume in your chosen unit plus the separate resin and hardener volumes.

Formula

The calculator uses the basic geometric volume formula for a rectangular prism:

Volume = Length × Width × Depth

For a cylinder, the formula is:

Volume = π × (Diameter / 2)² × Depth

After converting cubic inches to fluid ounces (1 cubic inch = 0.554 fluid ounces), the calculator adds the waste percentage:

Total Volume = Base Volume × (1 + Waste / 100)

Then it splits the total according to the mix ratio (R parts resin to 1 part hardener):

• Resin Volume = Total × (R / (R + 1))
• Hardener Volume = Total × (1 / (R + 1))

All volumes are in fluid ounces (US). To convert to milliliters, multiply by 29.574.

Worked Example

Using the default values: a slab 12 inches long, 8 inches wide, and 1.5 inches deep, with a 2:1 mix ratio and 10% waste.

1. Base volume in cubic inches: 12 × 8 × 1.5 = 144 in³
2. Convert to fluid ounces: 144 × 0.554 = 79.776 fl oz
3. Add 10% waste: 79.776 × 1.10 = 87.75 fl oz (rounded to 87.8)
4. Resin part: 87.75 × (2 / 3) = 58.5 fl oz
5. Hardener part: 87.75 × (1 / 3) = 29.25 fl oz

So for a 12×8×1.5-inch pour, you need about 87.8 fluid ounces of mixed epoxy, which means 58.5 oz resin and 29.25 oz hardener.

Why Mix Ratio Matters

Epoxy resins are two-part systems: the resin (part A) and the hardener (part B) undergo a chemical reaction when mixed. The ratio is determined by the manufacturer and is crucial. Too much hardener can cause the epoxy to cure too quickly, overheat, or become brittle. Too little hardener leaves the epoxy sticky or soft, and it may never fully cure. Always measure by volume or weight exactly as the manufacturer specifies—never guess.

The calculator lets you input the ratio from your product label. Common ratios are 1:1, 2:1, and 3:1 by volume, but some brands use weight ratios. If your ratio is by weight, convert to volume using the densities of the resin and hardener (usually printed on the technical data sheet).

How to Choose a Waste Allowance

Epoxy is viscous and sticks to mixing containers, stir sticks, and the sides of the pour area. You will lose some to transfer and some may remain in the mixing cup. A 10% waste allowance is typical for small projects. For larger pours or when working with intricate molds, increase it to 15–20%. If you are coating a flat surface with a thin layer, 5% may be enough.

Underestimating is a common mistake—you cannot just add more later because the new layer may not bond well. It is better to mix a little extra than to run out mid-pour.

Common Mistakes and How to Avoid Them

• Unit mix-ups: Mixing inches with centimeters or fluid ounces with milliliters. Always use the same unit system throughout.
• Forgetting the waste: Not adding a waste allowance leads to shortages, especially with deep pours.
• Incorrect ratio entry: If your ratio is 2:1, enter 2. If it is 1:1, enter 1. Do not enter the total number of parts (e.g., 3) as the ratio.
• Measuring by volume when ratio is by weight: Some epoxies specify a weight ratio. Using volume will give the wrong mix. Check the label.
• Rounding too early: Round only at the final step to avoid accumulating errors.

Limitations of the Calculator

This calculator gives a theoretical volume based on simple shapes. Real projects may have irregular shapes, sloped surfaces, or voids that require more epoxy. For complex molds, consider using a water displacement method: fill the mold with water, measure the water volume, and use that as your base volume.

Also, the calculator does not account for the slight volume change that occurs when resin and hardener are mixed. Most epoxies have a negligible shrinkage during mixing, but some may expand slightly due to trapped air. Degassing in a vacuum chamber can remove bubbles, but that is beyond the scope of volume calculation.

Safety and Handling Tips

Epoxy resins and hardeners can cause skin sensitization and allergic reactions. Always wear nitrile gloves (latex is not resistant) and safety glasses. Work in a well-ventilated area. If epoxy gets on your skin, wipe it off with a dry cloth, then wash with soap and water—do not use solvents. Read the safety data sheet (SDS) for your specific product. For deep pours, be aware that the exothermic reaction can generate significant heat; pouring too thick a layer can cause it to overheat, smoke, or crack. Follow the manufacturer’s maximum pour depth recommendations.

Frequently Asked Questions

How do I calculate epoxy for a round table?

Measure the diameter and the desired depth. Use the cylinder formula: Ï€ × (diameter/2)² × depth. For a 3-foot table (36 inches) with a 0.5-inch coating, that’s Ï€ × 18² × 0.5 = 508.9 in³, which is about 282 fl oz (or 8.3 liters). Add waste.

What if my mix ratio is by weight, not volume?

You need the densities of the resin and hardener. Multiply the volume of each component by its density to get the weight. Or, convert the weight ratio to a volume ratio using the formula: volume ratio = (weight ratio × density of hardener) / density of resin. Many brands provide both ratios on the label.

Can I mix a smaller batch than the calculator says?

Yes, but the ratio stays the same. If you need 10 oz total with a 2:1 ratio, you mix 6.67 oz resin and 3.33 oz hardener. The calculator can be used with any total volume—just adjust the dimensions or use the ratio alone.

Why is my epoxy still sticky after 24 hours?

This usually means the mix ratio was off, or the epoxy was mixed insufficiently. It can also happen if the temperature is too low. Some epoxies need a post-cure at a higher temperature. Check the product instructions. If it remains sticky, you may need to scrape it off and re-pour.

How do I convert fluid ounces to milliliters?

Multiply the fluid ounces by 29.574. For example, 87.8 fl oz × 29.574 = 2596 mL (about 2.6 liters).

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in l | Length | in | 12 | 0
in w | Width | in | 8 | 0
in d | Depth | in | 1.5 | 0
in ratio | Mix ratio (parts resin : 1 part hardener) | - | 2 | 0
in waste | Waste allowance | % | 10 | 0
out total | Total epoxy volume | fl oz | (l * w * d * 0.554) * (1 + waste / 100) | 1
out resin | Resin volume | fl oz | total * (ratio / (ratio + 1)) | 1
out hardener | Hardener volume | fl oz | total * (1 / (ratio + 1)) | 1