# Bioavailability Calculator (F = AUC_po · Dose_iv / AUC_iv · Dose_po) Calculate the absolute bioavailability F of an extravascular (typically oral) dose: F = (AUC_po · Dose_iv) / (AUC_iv · Dose_po), where AUC_po and AUC_iv are the areas under the concentration-time curve after oral and IV dosing, and the doses correct for any difference in amount administered. F is dimensionless and lies in [0, 1]; IV bioavailability is by definition 1, while oral F < 1 reflects incomplete absorption and/or first-pass metabolism. AUC can be in any consistent unit (e.g. mg·h/L) since it cancels out of the ratio. Valid only for linear pharmacokinetics, the same drug molecule, and doses within the linear range. Not medical advice. > Canonical page: https://elysiatools.com/en/tools/bioavailability-calculator - **Category:** Health - **Keywords:** bioavailability, absolute bioavailability, F, AUC, area under curve, first pass, oral absorption, fraction absorbed, pharmacokinetics, pk, drug, medicine ## Overview Calculate absolute bioavailability (F) for an oral or other extravascular dose using dose-corrected oral and IV AUC values: F = (AUC_po × Dose_iv) / (AUC_iv × Dose_po). The result is dimensionless and shown as a fraction and percentage. ## Inputs - **Oral AUC (mg·h/L)** (number): Area under the concentration-time curve after the oral dose. Must be positive. - **IV AUC (mg·h/L)** (number): Area under the concentration-time curve after the IV dose. Must be positive. - **Oral dose (mg)** (number): Oral dose administered. Must be positive. - **IV dose (mg)** (number): IV dose administered. Must be positive. - **Decimal Places** (number) ## When to use - Compare systemic exposure after oral and IV administration of the same drug molecule. - Correct an oral-to-IV AUC comparison when the administered doses are different. - Estimate absolute bioavailability under linear pharmacokinetic conditions. ## How it works - Enter the positive oral AUC, IV AUC, oral dose, and IV dose values. - The calculator applies F = (AUC_po × Dose_iv) / (AUC_iv × Dose_po). - AUC units cancel when the oral and IV values use consistent units, such as mg·h/L. - The result is reported as bioavailability F and as a percentage, with the selected number of decimal places. ## Use cases - Pharmacokinetic studies comparing oral and IV exposure. - Dose-corrected evaluation of oral absorption and first-pass effects. - Teaching and checking absolute bioavailability calculations from AUC data. ## Frequently asked questions ### What does the bioavailability result represent? It represents absolute bioavailability, or the fraction of an extravascular dose reaching systemic circulation relative to an IV dose. ### Which inputs are required? You need the oral AUC, IV AUC, oral dose, and IV dose. All four values must be positive. ### Do the oral and IV doses need to be equal? No. The formula adjusts for different doses. If the doses are equal, F simplifies to AUC_po divided by AUC_iv. ### What units should I use for AUC? Use any consistent AUC unit for both measurements, such as mg·h/L. The AUC units cancel in the ratio. ### When is this calculation valid? It is intended for the same drug molecule, linear pharmacokinetics, and doses within the linear range. 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