Free tool

What's still in your system

Enter a half-life, your dose and your schedule. We'll draw the curve of how much of one dose is still active over time — as a percentage of a single dose, not a blood level.

This shows amount remaining as a percentage of one dose. It is not a blood level and not a recommendation.

Examples from Stack's compound library

Real half-life figures, cited from our own compound pages — tap one to fill the field above.

Peak / trough at steady state
—
how much higher the peak sits above the trough, once it levels off
Time to ~97% of steady state—
Steady-state peak—
Steady-state trough—

Stack keeps this running for you

The app plots this for everything in your stack automatically, using your real dose log instead of a hand-typed schedule.

Get the app

How the math works

Each dose decays on its own first-order curve: half of it is gone after one half-life, half of what's left after the next, and so on. The curve above is the sum of every dose you've taken so far, each decaying from the moment it was given — that's why it climbs and settles rather than resetting to zero between doses.

Peak/trough ratio at steady state = 2^(interval ÷ half-life). A short interval relative to a long half-life means the peak and trough sit close together; a long gap relative to a short half-life means they're far apart.

Time to steady state is about five half-lives, no matter the dose or the interval — that's the point where about 97% of the eventual plateau has been reached.

Not medical advice. This tool tracks and calculates. It does not show a blood level, and it does not recommend a compound, a dose, or a schedule — check any change with your prescriber.