What is volume of distribution?

Volume of distribution (Vd) is a hypothetical volume that describes how extensively a drug distributes into body tissues relative to plasma. It is not a real anatomical volume — values above the total body water (~42 L) indicate significant tissue binding.

What is the formula for Vd?

For an IV bolus dose: Vd = Dose / Cp, where Dose is in mg and Cp is the initial or steady-state plasma concentration in mg/L. The result is in liters.

What is a normal range for Vd?

Vd varies widely. Drugs confined to plasma have Vd ~3–5 L; those in extracellular fluid ~15 L; total body water ~42 L. Highly lipophilic drugs (e.g., chloroquine) can exceed 1000 L.

How is loading dose calculated from Vd?

Loading Dose = Vd × Target Cp. Enter your target plasma concentration in the optional field to compute this automatically.

What is the elimination rate constant (ke)?

ke = 0.693 / t½. It represents the fraction of drug eliminated per unit time. Clearance can then be derived as CL = ke × Vd.

Does this tool account for bioavailability?

No. The basic Vd formula assumes 100% bioavailability (IV administration). For oral or other routes, divide dose by bioavailability (F) before entering it.

Volume of Distribution Calculator

Name: Volume of Distribution Calculator
Availability: InStock
Author: Nham Vu

Calculate the volume of distribution (Vd) of a drug from its dose and steady-state plasma concentration.

Drug Parameters

Dose (mg) *

Plasma Concentration Cp (mg/L) *

Body Weight (kg) optional

Half-life t½ (hours) optional — enables CL & ke

Target Cp (mg/L) optional — for loading dose

Enter dose and plasma concentration, then click Calculate.

Summary

Calculate the volume of distribution (Vd) of a drug from its dose and steady-state plasma concentration.

How it works

Enter the drug dose (in mg) administered to the patient.
Enter the steady-state or peak plasma concentration (Cp) in mg/L.
Optionally enter the half-life and body weight for extended calculations.
Click Calculate to see Vd in liters and L/kg.
Review the derived metrics: loading dose, clearance, and elimination rate constant.

Use cases

Estimate Vd for IV bolus drugs in clinical or educational settings.
Determine a loading dose required to achieve a target concentration.
Understand drug tissue distribution for pharmacology coursework.
Compare Vd across drugs to predict tissue binding behavior.
Calculate drug clearance from Vd and half-life.
Support therapeutic drug monitoring (TDM) calculations.

Frequently Asked Questions

Last updated: 2026-06-13 · Reviewed by Nham Vu