Half-Life & Steady-State Estimator
See how a compound builds up in your system, when it reaches steady state, how much accumulates, and how long it takes to clear after your last dose.
Loading the steady-state estimator
Pick a compound or enter a half-life, dose, and dosing interval to see the time to steady state, accumulation ratio, peak and trough, and a washout curve.
How the steady-state estimate works
- 1Pick a compound or enter a half-life. Choose a preset to prefill its approximate half-life, or select Custom and type your own value in hours or days.
- 2Enter your dose and interval. Add the dose you take each time and how often you dose (for example every 24 hours or once a week).
- 3Read your steady-state results. See the time to steady state, accumulation ratio, and the estimated peak and trough amount in your body.
- 4Check the washout. The curve shows levels building over repeated doses and clearing after the last dose, with a days-to-clearance estimate.
Common questions
- How long does it take to reach steady state?
- A compound reaches roughly 97% of its steady-state level after about five half-lives, regardless of how often you dose. For semaglutide (about a 7-day half-life) that is roughly 35 days; for a peptide with a 2-hour half-life it is about 10 hours. Steady state means the amount you take in each interval matches the amount your body clears.
- What is the accumulation ratio?
- The accumulation ratio is how much higher your steady-state peak is compared with a single dose. It is calculated as 1 / (1 - e^(-k*T)), where k is the elimination rate and T is your dosing interval. Dosing more frequently relative to the half-life produces more accumulation, so a long-acting weekly compound accumulates far more than a short-acting one dosed daily.
- How do I estimate peak and trough levels?
- This tool models a single-compartment, first-order system with complete, instantaneous absorption. The steady-state peak is your dose multiplied by the accumulation ratio, and the trough is the peak decayed across one dosing interval. Values are shown as an amount in the body in your dose units, not a plasma concentration.
- How long until a compound clears after my last dose?
- After the last dose, levels fall by half every half-life. About five half-lives later roughly 97% has cleared. So a 7-day half-life compound is largely cleared about 35 days after the final injection, while a short-acting peptide clears within hours.
- Are these half-life values exact?
- No. Half-lives vary between individuals, routes of administration, and sources, and many research peptides have limited published data. Use the preset values as a starting point and enter a custom half-life when you have better information. This is an educational estimate, not medical advice.
Ready to draw your dose? Use the Dose & Reconstitution Calculator, or check your spend with the Cost-per-Dose Calculator.
For educational and research purposes only. Not medical advice.