Peptide half-life calculator
A mathematical demonstration, not research evidence for any compound.
Illustrative value
Illustrative half-life of 12 hours. Not a value for any compound.
Show chart data as a table
| Series | 1× t½ | 2× t½ | 3× t½ | 4× t½ | 5× t½ |
|---|---|---|---|---|---|
| Illustrative value | 12 hours · 50% | 24 hours · 25% | 36 hours · 12.5% | 48 hours · 6.25% | 60 hours · 3.125% |
1 half-life
12 hours
50% remaining
2 half-lives
24 hours
25% remaining
3 half-lives
36 hours
12.5% remaining
4 half-lives
48 hours
6.25% remaining
5 half-lives
60 hours
3.125% remaining
Idealized first-order elimination, R(t) = 100 × 2−t/t½. It ignores absorption, distribution, metabolites, individual physiology and effect duration, and is never a prediction for a person or a basis for timing anything.
The formula
R(t) = 100 × 2^(−t / t½)
- R(t) — idealized percentage of the starting amount remaining
- t — elapsed time
- t½ — elimination half-life, in the same unit as t
t = t½ × log₂(100 / R)
The inverse: the time for the idealized amount to fall to R percent. Half-lives of 1, 2, 3, 4 and 5 leave 50, 25, 12.5, 6.25 and 3.125 %.
Results are rounded for display only. How half-life works explains the model; for general unit and concentration arithmetic, see Best Peptide Calculator.
What it does not model
The curve is an idealized first-order elimination model. It is a mathematical illustration of what a half-life means, not a medical prediction. It does not model:
- Patient-specific pharmacokinetics
- Drug absorption from the site of administration
- Multi-compartment distribution
- Active metabolites
- Receptor occupancy
- How long a clinical effect lasts
- Individual blood concentrations
- Drug interactions
- Changes in kidney or liver function
Frequently asked questions
What does the calculator compute?
The fraction of a starting reference amount remaining after time t in an idealized first-order model, R(t) = 100 × 2^(−t / t½), plus the time to reach each of the first five half-lives.
How do I calculate the fraction remaining by hand?
Divide the elapsed time by the half-life to get the number of half-lives, n. The fraction remaining is 0.5 raised to the power n. For example, 2.5 half-lives leave 0.5^2.5 ≈ 17.7 %.
How long until 10 % remains?
In the idealized model, t = t½ × log2(100 / 10) ≈ 3.32 half-lives. For 1 % it is about 6.64 half-lives.
Can I use this to plan when to take something?
No. The calculator is a mathematical demonstration. It does not model absorption, distribution, metabolites, effect duration or any individual, and it produces no schedules or amounts.