TRT Dosage Calculator.
Turn a prescribed weekly testosterone dose into the exact injection volume and syringe reading. Enter your vial's concentration, your weekly milligrams, and how often you inject. This does the mg-to-mL-to-units math.
Frequently Asked Questions
How do I convert my weekly TRT dose in mg to mL?+
Divide the dose in milligrams by the concentration of your vial in milligrams per millilitre. At 200 mg/mL, a 100 mg weekly dose is 0.5 mL. This calculator does that conversion and then splits it across however many injections per week you actually take.
What do the units on an insulin syringe mean for testosterone?+
A U-100 insulin syringe is marked in units where 100 units equals 1 mL, so each unit is 0.01 mL. A 0.5 mL dose is 50 units on that barrel. The markings refer to volume, not to milligrams of testosterone. The same 50 units delivers a different dose from a 100 mg/mL vial than from a 200 mg/mL one, which is exactly the mistake this tool exists to prevent.
Does splitting the same weekly dose into more injections change anything?+
It changes the peaks and troughs, not the weekly total. Testosterone cypionate and enanthate have half-lives of roughly a week, so a single weekly injection produces a higher peak and a lower trough than the same amount split across two or three. Many people find more frequent, smaller injections steadier, but that is a clinical decision, not a mathematical one.
Why does vial concentration matter so much?+
Because it is the single most common source of a serious dosing error. 100 mg/mL and 200 mg/mL vials look identical and the same volume delivers double the dose from one to the other. Always read the concentration off the vial in front of you rather than assuming it matches your last prescription.
Is this calculator a substitute for a prescription or for blood work?+
No. It converts a dose your prescriber has already set into the volume and syringe markings for that dose. It cannot tell you what your dose should be. That comes from blood work, symptoms and a clinician, and testosterone therapy requires ongoing monitoring of haematocrit, oestradiol and PSA alongside testosterone itself.
The dose math, step by step.
Testosterone for injection is sold by concentration: milligrams of hormone per millilitre of oil, most commonly 100 or 200 mg/mL for cypionate and enanthate. Your prescription, though, is written in milligrams per week. This calculator bridges the two. First it divides your weekly dose by how many times you inject to get the milligrams per injection. Then it divides that by the vial concentration to get the volume in millilitres. Finally it converts millilitres to units on a U-100 insulin syringe, where 100 units equals exactly 1 mL.
A worked example: 140 mg per week, split into two injections, from a 200 mg/mL vial. That is 70 mg per injection, ÷ 200 mg/mL = 0.35 mL, which reads as 35 units on a U-100 syringe. The weekly total is 0.7 mL.
Why injection frequency matters.
The same weekly dose feels very different depending on how you split it. Long-ester testosterone (cypionate, enanthate) has a half-life of roughly 4–8 days, so a single large weekly shot produces a peak-and-trough curve: higher highs, lower lows, and often more mood and libido swing. Splitting the same weekly milligrams into two (every 3.5 days, "E3.5D") or into every-other-day injections flattens those swings and can reduce the rise in estradiol and hematocrit that drives many TRT side effects.
More frequent injections mean smaller volumes each time, which is why men on daily or EOD protocols use small U-100 insulin syringes rather than a larger intramuscular syringe. This calculator flags when your per-injection volume is too large for a 1 mL syringe or too small to measure accurately.
This is a reference, not a prescription.
Dose, ester, injection site, and schedule are individual medical decisions made with a prescriber who monitors your total and free testosterone, estradiol, hematocrit, and PSA. Testosterone raises red-blood-cell count and can suppress fertility; unmonitored use carries real cardiovascular and prostate considerations. Concentrations and pharmacy compounding also vary. Always confirm the number printed on your own vial.
Use this tool to check your arithmetic and understand what your prescribed dose translates to on the syringe, never to self-prescribe, adjust your dose without your clinician, or source testosterone outside a pharmacy.
- Bhasin S, Brito JP, Cunningham GR, et al. (2018). Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab, 103(5), 1715–1744.
- Morgentaler A, Traish A, Hackett G, et al. (2019). Diagnosis and treatment of testosterone deficiency: updated recommendations. World J Mens Health, 37(1), 7–24.
For education, not medical advice. Results are estimates, not a diagnosis. Discuss any abnormal value or health concern with a qualified clinician.
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