What this calculator does
The Epoxy Mix Ratio Calculator splits a desired total batch of epoxy into the correct amount of resin (Part A) and hardener (Part B) based on the manufacturer's mix ratio. Whether your product calls for 2:1, 1:1, 3:1, 5:1 or any custom ratio, this tool gives you exact quantities so the epoxy cures properly. It works for any unit — milliliters, ounces, grams or liters — and applies equally whether the ratio is specified by volume or by weight.
How to use it
Enter the total amount of mixed epoxy you need. Type the resin parts (R) and hardener parts (H) from your product label, then choose your unit. The calculator returns how much resin and hardener to combine to reach that total, plus the simplified R:1 ratio.
The formula explained
The ratio R:H means each batch is divided into \(R + H\) equal parts. The resin fraction is \(\frac{R}{R+H}\) and the hardener fraction is \(\frac{H}{R+H}\). Multiply each fraction by the total batch size to get the actual quantity. Because both fractions add to 1, the resin and hardener always sum back to your total.
$$\text{Resin} = \text{Total} \times \frac{R}{R+H}, \quad \text{Hardener} = \text{Total} \times \frac{H}{R+H}$$
Worked example
You need 150 ml of epoxy at a 2:1 ratio. Total parts = 2 + 1 = 3.
$$\text{Resin} = 150 \times \frac{2}{3} = 100 \text{ ml}$$$$\text{Hardener} = 150 \times \frac{1}{3} = 50 \text{ ml}$$Mix 100 ml resin with 50 ml hardener for exactly 150 ml.
FAQ
Is the ratio by volume or weight? Both work with this calculator, but volume and weight ratios are usually different — always read your label and don't swap one for the other.
What if I measure too much? Off-ratio epoxy may stay tacky or never fully cure. Measure carefully, ideally with graduated cups or a scale.
Can I scale a small test batch? Yes. Just enter a small total (e.g. 30 ml) and the same ratio to get a proportional mini-mix.
