Last updated: June 2026
Primobolan Dosage Calculator
Quick answer: A 200 mg/week dose over 2 shots from a 100 mg/mL vial is 1 mL (100 units) per shot, ≈ 146 mg active hormone/week. mL = (weekly mg ÷ shots) ÷ mg/mL.
Injectable ester — about 73% of each mg is Primobolan; the calculator converts dose → mL, units and active mg. Aromatises: No. Liver-strain (17α-alkylated): No. Half-life: ≈ 10.5 days (252 h).
About this calculator
Primobolan (methenolone enanthate) is a mild, DHT-derived long-ester injectable that does not aromatise. About 73% of each milligram is methenolone. This calculator converts a weekly dose into mL and U-100 units and shows the active-hormone milligrams delivered.
Methenolone is prized for a clean, low-side-effect profile, though it is mild per milligram so doses tend to be higher. The injectable enanthate is usually 100 mg/mL; an oral acetate version also exists.
How the injection-volume maths works
The long enanthate ester is over a quarter of the molecule’s weight, so 100 mg delivers about 73 mg of methenolone (302.5 ÷ 414.6). The calculator shows both the labelled dose and the active figure.
How to use this calculator
Enter your weekly dose, the concentration printed on your vial (mg/mL), and how many injections per week. The result updates instantly with the mL to draw, the U-100 syringe units, and the active-hormone milligrams delivered.
Worked examples
Weekly dose: 200 mg · Concentration: 100 mg/mL · Injections/week: 2
100 mg/shot ÷ 100 = 1 mL (100 units) · active ≈ 146 mg/week
Weekly dose: 400 mg · Concentration: 100 mg/mL · Injections/week: 2
200 mg/shot ÷ 100 = 2 mL (200 units) · active ≈ 292 mg/week
Primobolan dose chart
Common doses at 100 mg/mL, 2 injections/week (each row is the calculator’s arithmetic worked out):
| Weekly dose | mL/shot | Units | Active/week |
|---|---|---|---|
| 100 mg | 0.5 mL | 50 | 73 mg |
| 200 mg | 1 mL | 100 | 146 mg |
| 300 mg | 1.5 mL | 150 | 219 mg |
| 400 mg | 2 mL | 200 | 292 mg |
| 500 mg | 2.5 mL | 250 | 365 mg |
| 600 mg | 3 mL | 300 | 438 mg |
Half-life & clearance
Illustrative single-dose elimination by half-life (t½ ≈ 11 days). Each marker is one half-life; after ~5 the dose is essentially cleared. For an oil depot the real rise-and-fall is slower (absorption-limited release), so treat this as a timing reference, not a blood-level prediction.
With a long (~10.5-day) depot, Primobolan is injected infrequently and builds slowly over weeks. The figure comes from a pharmacology textbook (Westreich 2011) rather than a primary trial, so treat it as a reasonable estimate.
How to interpret your result
The result is the volume to draw per injection and its mark on a U-100 syringe. The active-hormone figure shows how much actual Primobolan that ester delivers — useful when comparing esters or switching concentrations. The half-life figure is a pharmacokinetic timing reference only.
Aromatisation, liver & monitoring
Methenolone does not aromatise, so it adds no estrogen. The injectable enanthate is not 17α-alkylated and so is not hepatotoxic — and unusually, the oral acetate form is also not 17α-alkylated.
Common mistakes
Underdosing because "Primo is mild" then expecting dramatic results is the common mismatch; it is genuinely gentle per milligram. For the maths, remember the active fraction is 0.73.
Primobolan at a glance
| Property | Primobolan |
|---|---|
| Form | Injectable (oil/suspension) |
| Active fraction | 0.73 (esterFactor) |
| Half-life | ≈ 10.5 days (252 h) — pharmacology textbook (Westreich 2011) |
| Aromatises | No — a DHT-derived compound, not an aromatase substrate. |
| Liver (17α-alkylated) | No — the injectable enanthate is a C17β ester, not 17α-alkylated. |
| Approx. detection | Several weeks+ (long ester). |
Frequently asked questions
Related guides
Other compounds
Other calculators
References
- PubChem — methenolone (molecular weight), CID 3037705
- PubChem — methenolone enanthate (molecular weight), CID 248271
- Kicman AT. Pharmacology of anabolic steroids. Br J Pharmacol 2008;154(3):502–521
Every citation URL was verified to return HTTP 200. Citations are provided for transparency and education and do not imply the cited authors or bodies endorse this tool. Anabolic steroid use carries real health risks — always consult a qualified clinician.
How this is calculated
For injectables the calculator divides your weekly dose by the number of injections, then by the vial concentration, to get the mL per shot — and multiplies by 100 for U-100 syringe units (1 mL = 100 units). The active-hormone milligrams are the dose multiplied by the esterFactor (the parent hormone’s molecular weight divided by the full ester’s molecular weight, both from PubChem). For orals it divides the daily dose by your doses-per-day and tablet strength to get tablets per dose. Half-life timing uses ke = ln2 ÷ t½ and the ~5-half-life rule of thumb for steady state and clearance. It is arithmetic only — nothing you enter is stored or sent anywhere, and the result is not medical advice or an endorsement of anabolic steroid use.