What does Km indicate?

Lower Km generally indicates higher apparent substrate affinity.

What happens when substrate concentration equals Km?

The reaction velocity is half of Vmax in the Michaelis-Menten model.

Can this model all enzymes?

No, only basic non-cooperative Michaelis-Menten behavior.

Do Km and Vmax have to use the same units?

Km and substrate concentration must use the same concentration unit. Vmax can use any rate unit as long as you interpret velocity in that same rate unit.

Enzyme Kinetics Calculator

Use Vmax, Km, and substrate concentration to estimate reaction velocity.

VmaxKm[S]

Formula

v = Vmax × [S] / (Km + [S])

Michaelis-Menten equation models enzyme-catalyzed reactions.

Symbol	Variable	Description
v	Velocity	Observed reaction rate.
Vmax	Maximum velocity	Rate at saturation.
Km	Michaelis constant	Substrate concentration at half Vmax.
[S]	Substrate concentration	Concentration of substrate.

How to Use the Enzyme Kinetics Calculator

1
Input Vmax
Use rate unit matching your assay.
2
Input Km and [S]
Use the same concentration unit for both.
3
Calculate
Read velocity and saturation fraction.

Michaelis-Menten Interpretation

The Michaelis-Menten calculator estimates reaction velocity for a simple enzyme system. Km is the substrate concentration where velocity is half of Vmax, so the saturation fraction helps you see whether the reaction is substrate-limited or near saturation.

When [S] equals Km, v is 50% of Vmax.
When [S] is much lower than Km, velocity is sensitive to substrate concentration.
When [S] is much higher than Km, velocity approaches Vmax.
Lower Km often suggests higher apparent substrate affinity under the assay conditions.

When This Model Fits

Use this enzyme kinetics calculator for basic Michaelis-Menten behavior, classroom problems, and quick assay planning. It assumes a single substrate, steady-state conditions, and no cooperative binding or strong inhibition effects.

Best for non-cooperative enzyme kinetics.
Not suitable for allosteric enzymes without a more specific model.
Inhibitors, pH, temperature, enzyme instability, and substrate depletion can change observed velocity.
Use consistent units for Vmax, Km, and substrate concentration.

Common Enzyme Kinetics Checks

Before trusting calculated velocity, make sure your experimental values come from an initial-rate region. Enzyme assays are usually interpreted using early time points where product accumulation, substrate depletion, and reverse reactions are limited.

Use initial velocity when fitting Km and Vmax.
Avoid saturated detector signals or endpoint-only readings for kinetic interpretation.
Replicates and blanks are needed for reliable assay conclusions.

Enzyme Kinetics FAQ

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