Binding Kinetics Calculator
Calculate KD, kobs, occupancy, and residence time from kon, koff, and ligand concentration.
Binding kinetics results
Enter finite values greater than zero.
Assumes reversible 1:1 single-step binding with effectively constant free ligand. Residence time is a population mean, not an exact dissociation time for each complex. Raw sensorgram fitting, ligand depletion, rebinding, mass transport, multisite binding, and cooperativity are outside this calculator.
Source: NIH/NCATS Assay Guidance Manual, “Analyzing Kinetic Binding Data” (NBK569501).
Tool Guide
Definition
Binding Kinetics Calculator — For reversible 1:1 single-step binding, use kon, koff, and free ligand concentration to calculate kinetic KD, kobs, equilibrium occupancy, residence time, and half-lives.
Purpose
(1) Cross-check reported kon and koff from SPR/BLI or direct-binding assays (2) Compare affinity and dissociation persistence across compounds (3) Estimate equilibrium occupancy and approach time at a ligand concentration (4) Prepare converted units and derived values for reports
How to Use
① Enter kon (M⁻¹s⁻¹), koff (s⁻¹), and free ligand concentration. ② Choose KD concentration and time display units. ③ KD=koff/kon, kobs=kon[L]+koff, and time-derived values update instantly. This tool does not fit raw sensorgrams. Model mismatch, ligand depletion, rebinding, and mass-transport limitation require separate analysis.
Examples
Example) kon=1×10⁶ M⁻¹s⁻¹, koff=0.001 s⁻¹, [L]=10 nM → KD=1 nM, kobs=0.011 s⁻¹, equilibrium occupancy=90.91% → residence time=16.67 min, dissociation half-life=11.55 min, association half-life=1.05 min