OptiPin
Half-life calculator
See how much testosterone, anabolics, peptides or GLP-1s are actually in your system over time, in mg or mcg, at steady state or from a single dose, using published half-life and time-to-peak values for 66 compounds. Full reference table below.
This web tool uses one shared one-compartment (Bateman) curve to illustrate timing. The OptiPin app runs more advanced, compound-specific models and personalizes them to you:
- Testosterone uses a saturation-then-decay absorption model calibrated per ester, layered on your endogenous baseline - then recalibrated to your bloodwork and converted to a free-testosterone estimate shown against reference ranges.
- Estradiol esters use a separate absorption-scaled model tuned to each formulation, also calibrated to your labs.
- Peptides, GLP-1s, and anabolics use compound-specific pharmacokinetics with evidence-quality flags, so weakly-characterized compounds are marked as estimates.
This page estimates how much compound is in your system in mg or mcg. The app goes further and outputs personalized blood levels in clinical units, calibrated to your own bloodwork.
See your levels in OptiPin
OptiPin forecasts testosterone, estrogen, DHT, and GLP-1 levels from your actual logged doses and calibrates to your bloodwork - all on-device, no cloud required.
Download on the App StoreHalf-life reference table
Every compound in the calculator, with its published half-life and the two numbers people actually want from it: how long regular dosing takes to plateau (about 4.3 half-lives, ~94% of steady state) and how long it takes to clear after the last dose (about 5 half-lives, ~97% eliminated). Where we have a full compound profile, the name links to it.
| Compound | Route | Half-life (t½) | Time to steady state | Cleared after stopping | Evidence |
|---|---|---|---|---|---|
| Testosterone & esters | |||||
| Trestolone (MENT) | IM | 53 days | 229 days | 265 days | Limited |
| Testosterone Undecanoate (Castor) | IM | 34 days | 146 days | 170 days | Strong |
| Testosterone Undecanoate (MCT) | IM | 20 days | 86 days | 100 days | Estimated |
| Testosterone Enanthate | IM | 7.2 days | 31 days | 36 days | Strong |
| Testosterone Isocaproate | IM | 7 days | 30 days | 35 days | Moderate |
| Testosterone Cypionate | IM | 6.9 days | 30 days | 34 days | Strong |
| Testosterone Decanoate | IM | 5.6 days | 24 days | 28 days | Moderate |
| Testosterone Gel | Transdermal | 3 days | 12.9 days | 15 days | Strong |
| Testosterone Phenylpropionate | IM | 2.5 days | 10.8 days | 12.5 days | Moderate |
| Testosterone Suspension | IM | 1.4 days | 6 days | 6.9 days | Moderate |
| Testosterone Propionate | IM | 1 days | 4.5 days | 5.2 days | Strong |
| Testosterone Undecanoate (Oral) | Oral | 18.5 h | 3.3 days | 3.9 days | Strong |
| Trestolone Acetate | IM | 3.8 h | 16.6 h | 19.2 h | Limited |
| Testosterone Base (Sublingual) | Sublingual | 37 min | 2.7 h | 3.1 h | Limited |
| Estrogen & progesterone | |||||
| Estradiol Valerate | IM | 14 days | 60 days | 70 days | Strong |
| Estradiol Cypionate | IM | 10 days | 43 days | 50 days | Strong |
| Estradiol Gel (EstroGel) | Transdermal | 2 days | 8.6 days | 10 days | Strong |
| Progesterone (Oral) | Oral | 22.8 h | 4.1 days | 4.8 days | Strong |
| Progesterone (Vaginal) | vaginal | 20.6 h | 3.7 days | 4.3 days | Strong |
| GLP-1 agonists | |||||
| Mazdutide | SubQ | 18 days | 78 days | 90 days | Estimated |
| Semaglutide | SubQ | 6.5 days | 28 days | 32 days | Strong |
| Survodutide | SubQ | 6.5 days | 28 days | 32 days | Estimated |
| Retatrutide | SubQ | 6.1 days | 27 days | 31 days | Moderate |
| Tirzepatide | SubQ | 4.9 days | 21 days | 24 days | Strong |
| Peptides & growth hormone | |||||
| HCG | SubQ | 2 days | 8.5 days | 9.8 days | Strong |
| TB-500 | SubQ | 4.8 h | 20.7 h | 1 days | Limited |
| HGH (Somatropin) | SubQ | 4.1 h | 17.6 h | 20.4 h | Moderate |
| BPC-157 | SubQ | 3.6 h | 15.6 h | 18 h | Limited |
| Injectable anabolics | |||||
| Trenbolone Enanthate | IM | 11 days | 48 days | 55 days | Moderate |
| Primobolan (Injectable) | IM | 10.5 days | 45 days | 52 days | Moderate |
| Nandrolone Decanoate (Deca) | IM | 10.2 days | 44 days | 51 days | Strong |
| Dihydroboldenone (DHB) | IM | 9 days | 39 days | 45 days | Limited |
| Trenbolone Hex (Parabolan) | IM | 8 days | 35 days | 40 days | Moderate |
| Boldenone Cypionate | IM | 6.9 days | 30 days | 34 days | Estimated |
| Boldenone Undecylenate (EQ) | IM | 5.1 days | 22 days | 26 days | Moderate |
| Masteron Enanthate | IM | 4.5 days | 19 days | 22 days | Limited |
| Nandrolone Phenylpropionate (NPP) | IM | 2.4 days | 10.4 days | 12 days | Moderate |
| Masteron Propionate | IM | 2 days | 8.6 days | 10 days | Moderate |
| Trenbolone Acetate | IM | 1.5 days | 6.5 days | 7.5 days | Moderate |
| Oral steroids | |||||
| Winstrol Injectable | IM | 3.4 days | 15 days | 17 days | Moderate |
| Turinabol (Tbol) | Oral | 16.1 h | 2.9 days | 3.4 days | Moderate |
| Proviron (Mesterolone) | Oral | 12.5 h | 2.2 days | 2.6 days | Moderate |
| Superdrol (Methasterone) | Oral | 10.1 h | 1.8 days | 2.1 days | Limited |
| Winstrol Oral (Stanozolol) | Oral | 9 h | 1.6 days | 1.9 days | Moderate |
| Anadrol (Oxymetholone) | Oral | 7.9 h | 1.4 days | 1.7 days | Moderate |
| Anavar (Oxandrolone) | Oral | 6.7 h | 1.2 days | 1.4 days | Strong |
| Dianabol (Methandrostenolone) | Oral | 5.3 h | 22.8 h | 1.1 days | Moderate |
| Primobolan (Oral) | Oral | 5 h | 21.8 h | 1.1 days | Moderate |
| Halotestin (Fluoxymesterone) | Oral | 2 h | 8.6 h | 10 h | Moderate |
| SARMs | |||||
| Testolone (RAD-140) | Oral | 1.9 days | 8 days | 9.3 days | Limited |
| Ligandrol (LGD-4033) | Oral | 1.2 days | 5.4 days | 6.2 days | Moderate |
| Ostarine (MK-2866) | Oral | 1 days | 4.3 days | 5 days | Moderate |
| Cardarine (GW-501516) | Oral | 19.9 h | 3.6 days | 4.1 days | Limited |
| S-23 | Oral | 4.1 h | 17.6 h | 20.4 h | Limited |
| Andarine (S4) | Oral | 3.8 h | 16.6 h | 19.2 h | Limited |
| Aromatase inhibitors & SERMs | |||||
| Clomiphene (Clomid) | Oral | 5 days | 22 days | 25 days | Strong |
| Cabergoline (Caber) | Oral | 3.6 days | 15 days | 18 days | Strong |
| Tamoxifen (Nolvadex) | Oral | 2 days | 8.6 days | 9.9 days | Strong |
| Anastrozole (Arimidex) | Oral | 1.9 days | 8.4 days | 9.8 days | Strong |
| Letrozole (Femara) | Oral | 1.4 days | 6 days | 6.9 days | Strong |
| Exemestane (Aromasin) | Oral | 22.8 h | 4.1 days | 4.8 days | Strong |
| Other pharmaceuticals | |||||
| DNP | Oral | 3.7 days | 16 days | 18 days | Limited |
| Clenbuterol | Oral | 1.1 days | 4.8 days | 5.6 days | Moderate |
| Telmisartan | Oral | 23.3 h | 4.2 days | 4.8 days | Strong |
| Nebivolol | Oral | 17 h | 3.1 days | 3.5 days | Strong |
| Tadalafil (Cialis) | Oral | 17 h | 3.1 days | 3.5 days | Strong |
Evidence reflects how well-characterised the pharmacokinetics are in published human data. Strong means values come from controlled PK studies; limited means they are extrapolated from sparse or animal data and should be treated as rough. Values are population averages - your own clearance depends on body composition, injection site, ester carrier and liver function.
Why half-life matters more than dose size
It sets your injection frequency. A compound is dosed relative to its half-life, not its strength. Testosterone propionate (t½ ~1 day) needs every-other-day injections to stay stable; cypionate (t½ ~6.9 days) tolerates weekly or twice-weekly. Inject a short ester weekly and you get a peak-and-crash curve regardless of how much you use.
It tells you when bloodwork is meaningful. Testing before steady state measures a level that is still climbing. For testosterone cypionate that means waiting roughly 30 days after starting or changing a dose; for testosterone undecanoate in castor oil, closer to five months. Draw earlier and you will under-read your own protocol.
It sets the washout after stopping. The same arithmetic runs backwards. Five half-lives is the practical clearance figure - days for an oral like Anavar, over a month for a long-ester injectable, and longer still for undecanoate. This is what determines how long a change takes to show up in how you feel.
It explains accumulation. If you dose more often than your compound clears, each dose lands on top of the residue of the last. That accumulation is why steady-state levels sit well above the peak of a first dose, and it is the part people most often underestimate. The calculator above opens on steady state, so the gap for your own interval is the first thing it shows you.
Frequently asked questions
What is the half-life of testosterone cypionate?
About 6.9 days, with a peak around 4.5 days after an intramuscular injection. That puts steady state at roughly 30 days of regular dosing and full clearance at about 34 days after the last shot. Enanthate is very close at ~7.2 days; propionate is far shorter at ~1 day.
How do I calculate a testosterone half-life?
You do not calculate the half-life itself - it is a measured property of the ester, taken from published pharmacokinetic studies. What you calculate from it is time to steady state (about 4.3 half-lives) and time to clear (about 5). Select your ester above and the calculator plots the curve from its published half-life and time to peak.
What is the half-life of Anavar?
Oxandrolone sits at roughly 6.7 hours, which is why it is dosed daily rather than weekly. It reaches steady state in a little over a day and clears in under two after the last dose. Most oral steroids are in this range, and that gap is the main practical difference between orals and injectables.
Do peptides have half-lives too?
Yes, usually far shorter than steroid esters. BPC-157 is around 3.6 hours and HGH about 4 hours. The GLP-1 agonists are the exception at roughly 5-7 days for tirzepatide, semaglutide and retatrutide, which is why they are dosed weekly while most repair peptides are dosed daily or more often.
How long until a compound reaches steady state?
With regular dosing, blood levels reach about 94% of steady state after 4 half-lives and ~97% after 5. For testosterone cypionate that is roughly 4-5 weeks; for a short ester like propionate, a few days. The reference table above lists this for every compound.
What does the curve represent?
The estimated amount of compound still in your system over time, in the same unit as your dose, using a one-compartment pharmacokinetic model (Bateman function) with the compound's published half-life and time to peak. Because each dose lands on the residue of the last, steady-state levels sit well above a single dose peak. It is an amount in the body, not a blood concentration in ng/dL, and it is an educational model rather than a personalized prediction.
How long until a compound fully clears after stopping?
After the last dose, a compound is effectively cleared after about 5 half-lives (~97% eliminated). For testosterone cypionate that is roughly 5 weeks; for propionate, about a week. Long esters like undecanoate take months.
How to read this
Half-life is the time for blood levels of a single dose to fall by half. A longer half-life means slower clearance and more accumulation with repeat dosing.
Steady state is reached after about 4–5 half-lives of regular dosing - that's when the amount you take each interval roughly equals the amount cleared. Levels then oscillate between a peak and trough. Shorter intervals relative to half-life produce a flatter curve.
Full clearance is the mirror image: after your last dose, a compound is effectively gone after about 5 half-lives (~97% eliminated). For a long ester this can be over a month; for a short one, days.