Michaelis-Menten Kinetics Calculator

Calculate enzyme reaction velocity, Vmax, Km, and enzyme efficiency using Michaelis-Menten kinetics.

Substrate concentration [S] (mM) (mM)

Maximum velocity Vmax (μmol/min) (μmol/min)

Michaelis constant Km (mM) (mM)

Enzyme concentration [E] (μM, optional) (μM)

For kcat calculation

Please check your inputs and try again.

Worked Examples

Example 1: [S]=5mM, Vmax=100, Km=2mM

v=100×5/(2+5)

Result: 71.4 μmol/min — 71.4% Vmax

Above Km, enzyme is well-saturated

Example 2: [S]=0.2mM (<

v=100×0.2/2.2

Result: 9.1 μmol/min — linear range

At [S]<

Frequently Asked Questions

What does Km represent?

Km is the substrate concentration at which reaction rate = Vmax/2. It approximates the affinity of the enzyme for its substrate — lower Km means higher affinity.

What is catalytic efficiency kcat/Km?

kcat/Km (specificity constant) measures how efficiently an enzyme converts substrate at low [S]. Maximum theoretical value: ~10⁸–10⁹ M⁻¹s⁻¹ (diffusion limit). Used to compare enzyme variants.