Catalytic Activity Converter
Catalytic activity measures how fast a catalyst, often an enzyme, converts substrate. The SI unit is the katal, one mole per second. Laboratories also use the older enzyme unit U, one micromole per minute. Enter a value, pick the units, and the converter applies exact SI definitions. The base unit is the katal.
How the conversion works
value in kat = value * (from factor)
result = value in kat / (to factor)
1 kat = mol/s; 1 U = 1 umol/min
Each factor is the unit's size in katals. The input is converted to katals, then to the target unit.
Worked example
1 U equals one micromole per minute, which is 10^-6 divided by 60 katals, about 1.667e-8 kat. Dividing by the nanokatal factor (10^-9) gives about 16.67 nkat.
Catalytic activity: frequently asked questions
What is the katal?
The katal is the SI derived unit of catalytic activity, defined as one mole of substrate converted per second. It applies to enzymes and other catalysts. Its symbol is kat, and it equals moles per second.
What is the enzyme unit U?
The enzyme unit, symbol U, is an older unit defined as the amount of enzyme that converts one micromole of substrate per minute. One U therefore equals one micromole per minute, which is 1 divided by 60 microkatals, or about 16.67 nanokatals.
How do I convert U to katal?
One U is one micromole per minute. Convert micromoles to moles (times 10 to the power minus 6) and minutes to seconds (divide by 60): 1 U equals 10 to the power minus 6 divided by 60 katals, about 1.667 times 10 to the power minus 8 katals.
Why was the katal introduced?
The katal was adopted by the General Conference on Weights and Measures in 1999 to give catalytic activity a coherent SI unit based on the second, replacing the inconsistent use of the per-minute enzyme unit. Both are still seen in laboratory practice.
Official sources
- BIPM SI Brochure, the katal: bipm.org.
- NIST Guide to the SI: nist.gov SP 811.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.