With this calculator you can easily work out the desired weights required to make up any two-part mixture that is given as a ratio. The most common being epoxy resin which is made up of a resin and a hardner, but this can also apply to other mixtures, such as silicone rubber for moulds.

Using an accurate pair of scales it is easier to work out the amounts needed by weight rather than volume, there are two methods for weighing out your desired quantity; with three cups measure out the resin and hardener separately and then mix together in the third. Or with a single cup weigh out the larger of the ratio, normally the resin, and then top up with the hardner to your desired weight and then mix.

The weight ratios are calculated thusly:

- Resin Weight = (resin ratio / (resin ratio + hardner ratio)) x desired weight
- Hardner Weight = (hardner ratio / (resin ratio + hardner ratio)) x desired weight

To calculate the amount you will need, in metric, you will need work out the size of the volume you wish to fill, convert that to the capacity and finally convert to the required weight:

- Total Weight = (Width x Height x Depth) / 1000
*divide by a thousand when mesuring in millimeters* - eg: 100mm Wide x 130mm High x 6mm Deep = 78000mm
^{3} - Now divide 78000/1000 to give you a capacity of 78mL, which is 78 grams
- and using the calculator with an epoxy ratio of 10:1, this gives us needing: 70.9g of resin and 7.1g of hardner