Free tool · Testosterone dose calculator
Testosterone dose & syringe calculator. mg to mL to units, instantly.
Enter the concentration printed on your vial and the dose you were prescribed. The calculator converts milligrams to mL and to insulin-syringe units for U-100, U-50 and U-40 barrels — the same arithmetic the TRT AI iPhone app runs before every logged shot. It converts a dose you already have; it does not suggest one.
The number printed on the vial label — e.g. Testosterone Cypionate 200 mg/mL.
Your prescribed per-injection dose in milligrams.
U-100: 100 units per mL. U-50: 50-unit half-mL barrel. U-40: 40 units per mL.
Your draw
Draw 50 units (0.5 mL)
The math
- ConcentrationPre-mixed concentration: 200 mg/mL
- mL to draw100 mg ÷ 200 mg/mL = 0.5 mL
- Syringe units0.5 mL × 100 units/mL = 50 units
Made with TRT AI · trtai.app
How the conversion works
Pre-mixed testosterone esters state their concentration directly on the vial — 100, 200 and 250 mg/mL are the common strengths, and the FDA-approved label for testosterone cypionate lists 100 mg/mL and 200 mg/mL. Your draw volume is dose ÷ concentration: a 100 mg dose from a 200 mg/mL vial is 0.5 mL. Insulin syringes are marked in units rather than millilitres, so that volume is then scaled by the syringe’s units-per-mL.
The two lines of arithmetic
- mL to draw = dose (mg) ÷ concentration (mg/mL)
- Syringe units = mL to draw × (syringe units ÷ syringe volume in mL)
A U-100 syringe holds 100 units in 1.0 mL, so it reads 100 units per mL. A U-50 holds 50 units in 0.5 mL — also 100 units per mL, but in a smaller barrel with finer gradations. A U-40 holds 40 units in 1.0 mL, so it reads 40 units per mL. That last one is the trap: the same physical volume shows a completely different number.
Worked examples
| Dose | Vial | Syringe | Volume | Reads as |
|---|---|---|---|---|
| 100 mg | 200 mg/mL | U-100 | 0.5 mL | 50 units |
| 100 mg | 200 mg/mL | U-40 | 0.5 mL | 20 units |
| 80 mg | 250 mg/mL | U-100 | 0.32 mL | 32 units |
| 50 mg | 100 mg/mL | U-100 | 0.5 mL | 50 units |
| 40 mg | 200 mg/mL | U-50 | 0.2 mL | 20 units |
Rows one and two are the point of the whole tool: an identical dose from an identical vial, and the number on the barrel differs by a factor of 2.5 purely because of the syringe scale.
Assumptions, and what this calculator does not do
- Pre-mixed oil only. The vial strength is the concentration. There is no reconstitution step, so this is not a peptide or lyophilised-powder calculator.
- No dead space. Volume left in the needle and hub is not modelled, and it varies by needle and technique.
- Display rounding. Units are shown to one decimal place and millilitres to three, matching the app.
- Sanity warnings, not judgements. The tool flags a concentration above 500 mg/mL, a dose below 0.5 mg or above 1000 mg, and any draw that exceeds the selected barrel — as prompts to re-read the vial, not as clinical opinions.
- No dose suggestions, ever. It converts the number you were prescribed. What that number should be is a decision for your prescriber.
Where the mistakes actually happen
- Reading a U-40 barrel as if it were U-100 (or the reverse).
- Confusing units with millilitres — 50 units on a U-100 syringe is 0.5 mL, not 50 mL.
- Confusing the vial’s concentration (mg/mL) with its total content (e.g. 2000 mg in a 10 mL vial at 200 mg/mL).
- Carrying an old volume over after a pharmacy switches you between 200 and 250 mg/mL.
If you want to understand what the ester does after the draw — accumulation, steady state and peak-to-trough swing — that is the injection frequency guide and the half-life calculator.
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