A compound is considered effectively cleared after about five half-lives, when roughly 97% has been eliminated. Enter an elimination half-life below to see the percentage remaining at any point, the time to full clearance, and how much accumulates if you dose repeatedly.
A math tool, not medical advice.
This calculator only does arithmetic on the numbers you type. It does not recommend a dose, a schedule, a compound, or a supplier. Most peptides are not FDA-approved and many have no legal supervised route at all. Check how we grade the evidence and talk to a licensed clinician.
Use hours for short-acting peptides, days for the weekly GLP-1 class. Every field below uses this unit.
hours
From the compound's own pharmacokinetic data or FDA label. We do not supply this number, so check a primary source and note that many research peptides only have animal estimates.
hours
To see how much is still theoretically present.
hours
The gap between repeat doses, to estimate accumulation. Enter the interval you were given. We do not suggest one.
The math
Enter an elimination half-life to see the decay curve, the time to effectively full clearance, and how much accumulates on repeat dosing.
Single-compartment first-order decay, the standard textbook model. Real clearance varies with kidney and liver function, body composition, dose, and route, and many research peptides have only animal-derived estimates. This is not a washout schedule, a pre-surgery hold, or medical advice.
How the half-life math works
Elimination follows first-order kinetics, meaning a constant fraction is removed per unit time rather than a constant amount. That gives an exponential decay curve:
Because it is exponential, the drop is front-loaded: half of the total elimination happens in the first half-life alone. That is why people often feel a change quickly after stopping, while a measurable trace persists far longer.
Why we do not fill in the half-life for you
Half-life figures for research peptides vary widely by source, and many come from animal models rather than human pharmacokinetic studies. Publishing a single authoritative number per compound would imply a confidence the underlying literature does not support. Take the figure from the compound's FDA label where one exists, or from the primary study, and check what tier of evidence it rests on using our A to F grading rubric.
What this calculator does not model
It uses a single-compartment model, the standard textbook simplification. It does not account for distribution phases, active metabolites, saturable clearance, injection-site depot effects, or differences in kidney and liver function. For most questions of the form “roughly how long until this is gone,” the simple model is close enough. For clinical decisions, it is not.
FAQ
Frequently asked questions
How long does a peptide stay in your system?+
About five half-lives, which is when roughly 97% has been eliminated. The exact figure depends entirely on that compound's elimination half-life. A peptide with a 4-hour half-life is effectively cleared in about 20 hours; one with a 7-day half-life takes about 5 weeks. Enter the half-life above to see the full curve.
Why is five half-lives the standard for clearance?+
Because each half-life removes half of what remains. After one half-life 50% is left, after two 25%, after three 12.5%, after four 6.25%, and after five about 3%. Pharmacology treats roughly 97% elimination as clinically cleared, which is where the five-half-life convention comes from. It is a convention, not a hard boundary.
What does accumulation mean on repeat dosing?+
If you dose again before the previous dose has cleared, the amount in your system builds up until elimination balances intake. That plateau is called steady state and is typically reached after about four to five half-lives of repeated dosing. The accumulation factor shows how much higher the plateau sits than a single dose. A dosing interval shorter than the half-life produces more accumulation.
Do peptide half-lives from animal studies apply to humans?+
Often not directly. Many research peptides have only animal pharmacokinetic estimates, and half-life can differ substantially across species, routes of administration, and formulations. Where a compound has no human data, treat any half-life figure as an estimate with real uncertainty around it. Our compound pages state which grade of evidence each figure rests on.
Can I use this to plan a washout before surgery or pregnancy?+
No. This is textbook decay arithmetic on a number you enter, not a clinical washout schedule. Real clearance varies with kidney and liver function, body composition, dose, and route, and holding periods before procedures are set by clinical guidance rather than by a formula. That is a conversation with a licensed clinician.