Bioavailability Calculator
Calculate absolute or relative bioavailability from dose-normalized AUC values.
Bioavailability results
Enter positive AUC and dose values with matching dose bases (mass or mass/kg).
Both arms must use the same analyte, matrix, AUC interval, and analytical method. This tool does not integrate concentration-time data or perform log transformation, geometric mean ratios, 90% confidence intervals, or a bioequivalence decision. Review nonlinear PK, different study conditions, and substantial residual AUC separately.
Sources: FDA Bioavailability Studies Submitted in NDAs or INDs (2022); ICH M13A (2024).
Tool Guide
Definition
Bioavailability Calculator — Divide the dose-normalized AUC of a test administration by that of a reference administration. Absolute bioavailability compares an extravascular route with an IV reference; relative bioavailability compares a test formulation with a reference formulation.
Purpose
(1) Cross-check absolute F for oral, subcutaneous, or other extravascular routes (2) Compare relative F across development formulations (3) Prevent errors across mg/µg or mg/kg/µg/kg dose units (4) Prepare dose-normalized AUC ratios for PK reports
How to Use
① Select absolute or relative bioavailability. ② Choose the AUC interval (AUC₀–t or AUC₀–∞) and unit shared by both arms. ③ Enter AUC, actual administered dose, and dose unit for each arm. ④ Copy F fraction, F percent, and both dose-normalized AUC values. Both arms must share analyte, matrix, AUC interval, and analytical method. Mass doses cannot be mixed with body-weight-normalized doses.
Examples
Absolute F example) Oral AUC=80 at 100 mg; IV AUC=20 at 10 mg → Oral dose-normalized AUC=0.8 and IV=2 → F=0.4, absolute bioavailability=40% Relative F example) Test AUC=120 and reference AUC=100, both at 100 mg → relative bioavailability=120% This tool does not integrate AUC, calculate a GMR or 90% CI, or make a bioequivalence decision.