Steady-State Drug Concentration Calculator

Calculate the average steady-state plasma drug concentration (Css) using bioavailability, dose, clearance, and dosing interval.

Inputs

All fields required. Use consistent units (mg, L, hr).

Clearance Input Mode

Results

Enter values and click Calculate.

Formula Reference

Css = (F × Dose) ÷ (CL × τ)

CL = 0.693 × Vd ÷ t½

Cmin = Css × e(-k × τ)

Cmax = Css × (1 − e(-k × τ)) ÷ (1 − e(-k × τ))

For educational use only. Not for clinical decision-making.

Summary

Calculate the average steady-state plasma drug concentration (Css) using bioavailability, dose, clearance, and dosing interval.

How it works

  1. Enter the dose (mg) and dosing interval (hours).
  2. Set the bioavailability fraction F (0–1; use 1.0 for IV routes).
  3. Enter clearance (L/hr) directly, or switch to half-life mode and provide half-life and volume of distribution so CL is derived automatically.
  4. Click Calculate to see Css in mg/L along with minimum and maximum concentrations.
  5. Review the time-to-steady-state estimates (3.32 × t½ for 90%, 6.64 × t½ for 99%).
  6. Use the results for academic or instructional pharmacokinetics work only.

Use cases

  • Pharmacy students practicing pharmacokinetic calculations.
  • Educators demonstrating steady-state principles in lectures.
  • Researchers verifying manual PK computations.
  • Comparing how dosing intervals shift the steady-state level.
  • Understanding the impact of bioavailability on therapeutic exposure.
  • Estimating time to reach steady state for various drug half-lives.

Frequently Asked Questions

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