Enzyme Activity Calculator
Enzyme activity quantifies how fast an enzyme converts substrate. One enzyme unit forms one micromole of product per minute under defined conditions. This calculator turns your measured product, reaction time, assay volume, and protein content into total activity in units, volumetric activity in units per milliliter, and specific activity in units per milligram of protein, the standard measure of purity. All inputs are experimental, so you enter your own numbers and the tool applies the conventional definitions exactly.
Enzyme activity formulas
total activity (U) = product (umol) / time (min)
volumetric activity (U/mL) = U / assay volume (mL)
specific activity (U/mg) = U / total protein (mg)
Example: 50 umol in 10 min = 5 U
One unit is one micromole of product per minute. Keep units consistent: micromoles, minutes, milliliters, milligrams.
Enzyme activity context
- Total activity reflects how much enzyme work occurs per minute.
- Specific activity rises with purification as activity concentrates in less protein.
- The katal (mol/s) is the SI unit; 1 U equals about 16.67 nanokatal.
- All inputs are experimental measurements, not assumed values.
- A zero time or zero protein returns n/a for the affected output.
Enzyme activity: frequently asked questions
What is one unit of enzyme activity?
One enzyme unit (U) is the amount of enzyme that converts one micromole of substrate (or forms one micromole of product) per minute under defined assay conditions. Total activity in units equals micromoles of product formed divided by the reaction time in minutes.
What is specific activity?
Specific activity is enzyme activity per unit of total protein, usually expressed as units per milligram of protein. It is a measure of enzyme purity: as a preparation is purified, specific activity rises because activity is concentrated in less total protein.
How do I get volumetric activity?
Volumetric activity is total units divided by the assay volume, giving units per milliliter. It tells you how concentrated the active enzyme is in your solution, independent of how much protein is present.
Which inputs are experimental?
The amount of product formed, the reaction time, the assay volume, and the protein content all come from your experiment. This calculator does not assume any of these values; you enter your measured numbers and it applies the standard definitions.
What units should I use?
Enter product as micromoles, time in minutes, volume in milliliters, and protein in milligrams to get activity in units (U), volumetric activity in U/mL, and specific activity in U/mg, the conventional enzymology units.
Official sources
- NCBI Bookshelf: National Center for Biotechnology Information.
- NIST: National Institute of Standards and Technology.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.