Michaelis Menten Initial Rate Calculator
Calculate a non-inhibited single-substrate initial reaction rate from Vmax, Km and substrate concentration.
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Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Compute the substrate saturation fraction and scale by the entered maximum initial reaction rate.
v₀=Vmax[S]/(Km+[S])
Worked example
Vmax=100µmol/min, Km=2mM and substrate2mM give an initial rate50µmol/min, exactly half Vmax.
Assumptions and input details
Vmax and substrate must be nonnegative; Km must be positive. Substrate and Km share the selected molar-concentration basis. Vmax is entered total amount-per-time rate for the same assay volume and enzyme amount. This assumes single-substrate steady-state initial-rate kinetics without inhibition; no parameter fitting, substrate depletion, product inhibition, changing enzyme amount or biological dose is modeled.
References: NCBI Assay Guidance Manual: enzymatic assays
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
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The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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