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Katal (kat) to Enzyme units Converter

Enter a value in katal (kat) to convert it to enzyme units, microkatal.

How it is calculated

Both units measure catalytic activity, but with different time and amount bases. One katal is one mole of substrate converted per second; one enzyme unit (U) is one micromole per minute. Since 1 mol = 106 µmol and 1 min = 60 s, the factors are U = kat × 60,000,000 and µkat = kat × 1,000,000. The tool multiplies your katal value by those factors and shows each result to about four significant figures, dropping trailing zeros, so small inputs keep their detail (1.234567×10−8 kat shows as 0.7407 U). Results of 1,000 or more are shown as whole numbers. Zero and negative inputs are converted as they are, with no warning. Scientific notation such as 2.5e-6 is accepted.

Worked example

A purified enzyme preparation has an activity of 0.0000025 kat. Enzyme units: 0.0000025 × 60,000,000 = 150 U. Microkatal: 0.0000025 × 1,000,000 = 2.5, which the tool shows as 2.5 µkat. Check by hand: 2.5 µmol/s × 60 s/min = 150 µmol/min, which is 150 U. The two lines agree, as they must, since 1 µkat is always 60 U.

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Common mistakes

  • Confusing katal with microkatal. Typing a lab value of 5 µkat as 5 kat is a million-fold error; enter 0.000005 kat (or 5e-6) instead.
  • Forgetting that the time bases differ (seconds against minutes). Multiplying by 1,000,000 alone gives µkat, not U; the extra factor of 60 is needed for U.
  • Entering a negative or zero activity and reading the output as meaningful. The tool converts it without complaint, but a real activity is positive.
  • Comparing U with U/L or kat/L. This tool converts activity only; concentration units such as U/L also depend on the sample volume, which you must handle separately.

About this calculator

The katal (kat) is the SI unit of catalytic activity, defined as the amount of enzyme that converts one mole of substrate per second. It's enormous next to the traditional biochemistry unit, the enzyme unit (U) — one micromole of substrate converted per minute — so the exact relationship is 1 katal = 6 × 10⁷ enzyme units, which is also why lab work almost always uses microkatal (µkat) rather than the bare katal.

The katal was adopted as the SI-coherent unit by the CGPM in 1999, on the recommendation of IUPAC and IUBMB, but biochemists, clinical laboratories, and enzymology researchers still report activity in U or U/L on assay results and product datasheets out of decades-old convention, so converting between the two systems is a routine step when comparing data from an SI-based source against a traditional lab result.

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  • Editorial team

    One enzyme unit is a rate under defined assay conditions, usually stated with a temperature and pH, so the same preparation can quote different U values in different papers. Convert only figures measured under the same conditions. A quick check in your head: one U is about 16.7 nanokatal. If a conversion of your own looks off, post the starting value and what you expected.

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