Peptide Half-Life Calculator
Enter a half-life and elapsed time to see what percentage of the molecule remains. Pure pharmacokinetic arithmetic — the formula is shown.
25% remaining
After 2 half-lives, approximately 75% of the molecule has been eliminated.
Washout reference
Approximate elimination for a half-life of 120 minutes.
| Half-lives | Time elapsed | Remaining | Eliminated |
|---|---|---|---|
| 1 | 2 hr | 50% | 50% |
| 2 | 4 hr | 25% | 75% |
| 3 | 6 hr | 12.5% | 87.5% |
| 4 | 8 hr | 6.3% | 93.8% |
| 5 | 10 hr | 3.1% | 96.9% |
Pharmacokinetic arithmetic for research purposes — not medical advice. Actual elimination depends on individual metabolism, route of administration, and many other factors. The formula used: remaining = 0.5^(elapsed / half-life). This assumes first-order elimination.
Common peptide half-lives
Approximate half-lives from published literature. These are averages — individual results vary significantly by route, formulation, and biology.
| Peptide | Approximate half-life | Source |
|---|---|---|
| BPC-157 | Several hours (oral) / stable (local) | Varies by route |
| TB-500 (Thymosin β4) | ~2 weeks | Published PK estimates |
| Semaglutide | ~1 week | Novo Nordisk PI |
| Tirzepatide | ~5 days | Eli Lilly PI |
| Epitalon | ~12 minutes | Published PK |
| GHK-Cu | ~seconds to minutes (in serum) | Copper-binding kinetics |
Common questions
What is a half-life?
A half-life is the time it takes for half of a substance to be eliminated from the body (or a system). After one half-life, 50% remains. After two, 25%. After five, about 3%. The calculator uses the first-order elimination formula: remaining = 0.5^(elapsed / half-life).
How many half-lives does it take for a peptide to clear?
A common reference point is 5 half-lives, at which point roughly 97% of the molecule has been eliminated. The exact time depends on the specific peptide’s half-life. For a peptide with a 2-hour half-life, that is about 10 hours; for one with a 7-day half-life, that is about 35 days.
Does this account for individual metabolism?
No. This is the standard pharmacokinetic formula for first-order elimination, which is a mathematical model. Real-world elimination varies between individuals based on body composition, organ function, route of administration, and other factors. This is research-use arithmetic, not a clinical prediction.
What is first-order elimination?
First-order elimination means the rate of elimination is proportional to how much of the substance is present. Each half-life, the amount drops by 50% regardless of the starting amount. This is the standard model for most peptides and small molecules, though some substances follow different kinetics.