Drug-Receptor Binding Affinity Tool

Kd, Ki, IC50, receptor occupancy & binding curves

Binding Parameters

Enter only ONE of Kd, Ki, or IC50 — whichever you know.

Kd (nM)

Ki (nM)

IC50 (nM)

Ligand [L] (nM)

Bmax / Receptor Total (nM)

Example Drugs

Cheng-Prusoff Equation

Ki = IC₅₀ / (1 + [L*]/Km)

[L*] is the radioligand concentration used in the assay (here, your entered [L]); Km is that radioligand's own Kd for the receptor.

Key Formulas

Occupancy: [L]/(Kd+[L]) × 100%
Bound: Bmax × [L]/(Kd+[L])
Scatchard: Bound/Free = −Bound/Kd + Bmax/Kd