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Volume of Distribution Calculator (Vd)

· Last updated：2026-08-02

This tool is for informational purposes only and does not constitute medical, financial, or legal advice; consult a qualified professional for advice.

Calculate the apparent volume of distribution Vd in two modes. (A) One-compartment IV bolus: Vd = Dose / C0 (C0 = concentration extrapolated to t=0). (B) From clearance and half-life (linear kinetics): Vd = CL · t½ / 0.693. Vd is an APPARENT (theoretical) volume, not an anatomical one — highly tissue-bound drugs (digoxin ≈ 7 L/kg, amiodarone ≈ 66 L/kg) can exceed total body water, while highly plasma-protein-bound drugs (warfarin ≈ 0.14 L/kg) fall far below it. Optional body-weight input converts the result to L/kg. Note: Vd = Dose/C0 gives Vc (initial); Vss (steady state) and Vz (terminal) differ for multi-compartment models, and oral dosing returns Vd/F. Not medical advice.

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Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category
Health
Input types
select, number
Output type
json
Sample coverage
4
API ready
Yes

Overview

The Volume of Distribution Calculator estimates apparent Vd in liters using either an IV bolus dose and initial concentration C0 or clearance and elimination half-life. An optional body-weight input also reports Vd in L/kg.

When to use

  • Estimate Vd from an IV bolus dose and concentration extrapolated to time zero.
  • Calculate Vd from clearance and elimination half-life under linear kinetics.
  • Compare the result in liters and L/kg when body weight is available.

How it works

  1. 1Select the calculation mode: Dose/C0 or CL and t½.
  2. 2Enter the inputs required for the selected formula.
  3. 3Optionally enter body weight to calculate Vd per kilogram.
  4. 4The calculator returns Vd, the method used, and model notes in JSON format.

Use cases

  • Pharmacokinetic calculations using an IV bolus dose and extrapolated initial concentration.
  • Estimating apparent Vd from measured clearance and elimination half-life.
  • Normalizing Vd to body weight for pharmacokinetic comparisons.

Examples

1. Estimate Vd from an IV bolus

Pharmacokinetics student

Background

A 500 mg IV bolus produces an initial concentration of 10 mg/L. The learner wants to estimate the apparent volume of distribution and express it relative to a 70 kg body weight.

Problem

Calculate Vd using the one-compartment Dose/C0 method.

How to use

Select Dose/C0 mode, enter 500 for IV Dose, 10 for Initial concentration C0, and 70 for body weight.

mode: dose-c0; dose: 500 mg; c0: 10 mg/L; weight: 70 kg; decimalPlaces: 4

Outcome

The calculator returns Vd = 50 L and 0.7143 L/kg using Vd = Dose / C0. The result represents Vc, or the initial volume, in this model.

2. Calculate Vd from clearance and half-life

Clinical pharmacology trainee

Background

A drug has a clearance of 2.8 L/h and an elimination half-life of 8 hours. Body weight is available for an additional normalized result.

Problem

Estimate Vd from clearance and half-life under linear kinetics.

How to use

Select CL and t½ mode, enter 2.8 for clearance, 8 for half-life, and 70 for body weight.

FAQ

What formula does the Dose/C0 mode use?

It uses Vd = Dose / C0 for a one-compartment IV bolus calculation.

What formula does the CL and t½ mode use?

It uses Vd = CL · t½ / 0.693 under linear kinetics.

What units should I enter?

Enter dose in mg, concentration in mg/L, clearance in L/h, and half-life in hours. Body weight is entered in kg.

Can the calculator report Vd in L/kg?

Yes. Enter body weight to receive an optional Vd per kilogram result.

Is Vd a real anatomical volume?

No. Vd is an apparent theoretical volume and may differ substantially from anatomical body-fluid volumes. This calculator is not medical advice.

Hub

Pharmacokinetic Teaching and Dose-Model Checks

Explore pharmacokinetic formulas, model assumptions, and result consistency for teaching or QA without giving medication dosing or clinical advice.

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mode: cl-half; clearance: 2.8 L/h; halfLife: 8 h; weight: 70 kg; decimalPlaces: 4

Outcome

The calculator returns Vd = 32.3164 L and 0.4617 L/kg using Vd = CL · t½ / 0.693.