About the Catalyst Drops Calculator
This tool estimates how much catalyst to add to a resin or similar base material and converts that amount into an approximate number of drops. It is useful for hobbyists, makers, and technicians who know their batch volume, catalyst percentage, and dropper calibration.
How to use this calculator
- Enter the base material volume.
- Select the matching volume unit: US quart, US gallon, US fluid ounce, liter, or milliliter.
- Enter the catalyst ratio as a percent.
- Enter the dropper size in drops per mL.
- Choose Calculate Drops to see the estimated drops, mL, teaspoons, and comparison table.
- Choose Reset to return to the default 1 US quart, 1%, and 20 drops/mL values.
How it works
The calculator first converts the entered base material volume into milliliters using the selected unit. For example, 1 US quart is treated as 946.352946 mL, 1 US gallon as 3785.411784 mL, and 1 liter as 1000 mL.
It then finds catalyst volume with: catalyst mL = base mL × catalyst percent ÷ 100. The drop count is calculated as: drops = catalyst mL × drops per mL, then rounded to the nearest whole drop.
The teaspoon estimate is calculated by dividing catalyst milliliters by 4.92892159 mL per US teaspoon. The comparison table uses the same batch volume and dropper size, but shows common catalyst ratios of 0.5%, 1%, 1.5%, 2%, and 2.5%.
Results are educational mixing estimates. Always follow the resin or catalyst manufacturer’s instructions, use proper protective equipment, and measure carefully because catalyst strength, resin type, temperature, and dropper size can affect the correct amount.
Example calculation
For a 1 US quart batch at 1% catalyst with a 20 drops/mL dropper, the base volume is 946.35 mL. Catalyst volume is 946.35 × 0.01 = 9.46 mL. The drop estimate is 9.46 × 20 = 189.27, which rounds to about 189 drops, or about 1.92 teaspoons.
Frequently asked questions
How many drops of catalyst are in 1 mL?
The calculator default is 20 drops per mL, a common approximation. Actual droppers vary, so use your dropper’s measured drops per mL when accuracy matters.
What catalyst percentage should I use for resin?
Many resin systems use around 1% to 2%, but the correct percentage depends on the product, temperature, working time, and manufacturer instructions.
Why does the calculator reject catalyst percentages above 10%?
Percentages above 10% are unusually high for many catalyst mixing situations, so the calculator displays a warning to prompt you to check the product instructions before measuring.
Are drops accurate enough for catalyst mixing?
Drops are only an estimate because drop size depends on the dropper, liquid viscosity, and technique. For best accuracy, measure catalyst by volume or weight if your product instructions allow it.
Does this calculate catalyst by weight?
No. This calculator uses volume-based inputs and outputs milliliters, approximate teaspoons, and drops; it does not account for density or weight-based mix ratios.