Free TRT tool
TRT dose calculator
Testosterone replacement therapy (TRT) is prescribed in milligrams (mg), but you draw it up in milliliters (mL). Enter the dose your prescriber set and the strength printed on your vial to see the matching volume in mL and in syringe units.
Your numbers
How is your dose written?
The total mg for the week
Use the dose your prescriber set. This calculator converts units; it does not suggest doses.
Example values to try the math (50 to 200 mg per week). They are not suggestions.
Pick the schedule on your prescription. The calculator uses it only for the math.
The mg/mL number printed on your vial label. It tells you how many mg are in each mL.
An insulin syringe marked U-100 holds 100 units in 1 mL. Other syringes are marked in mL.
Results
Enter your numbers to see the result.
Draw per injection
Enter your numbers to see the result.
Syringe (U-100, 1 mL)
The picture fills in once the dose, schedule and vial strength are entered.This syringe has a mark every 2 units. Brands differ, so check the marks on your own syringe.
Worked examples
These rows show the math for some weekly totals from 100 to 200 mg, each split into 1 or 2 injections. They are arithmetic examples, not suggested doses or schedules.
| Weekly total | Injections per week | Dose per injection | Volume | U-100 units |
|---|---|---|---|---|
| 100 mg | 1 | 100 mg | 0.5 mL | 50 |
| 2 | 50 mg | 0.25 mL | 25 | |
| 120 mg | 1 | 120 mg | 0.6 mL | 60 |
| 2 | 60 mg | 0.3 mL | 30 | |
| 140 mg | 1 | 140 mg | 0.7 mL | 70 |
| 2 | 70 mg | 0.35 mL | 35 | |
| 160 mg | 1 | 160 mg | 0.8 mL | 80 |
| 2 | 80 mg | 0.4 mL | 40 | |
| 200 mg | 1 | 200 mg | 1 mL | 100 |
| 2 | 100 mg | 0.5 mL | 50 |
How the math works
The calculator does four simple steps. Here they are with one example: 120 mg per week, 2 injections per week and a 200 mg/mL vial.
Split the weekly dose
mg per injection = weekly mg ÷ injections per week
120 ÷ 2 = 60 mg
Turn mg into mL
mL = mg ÷ vial strength (mg/mL)
60 ÷ 200 = 0.3 mL
Turn mL into syringe units
units = mL × 100 (U-100 syringes only)
0.3 × 100 = 30 units
Count the weeks in a vial
weeks = vial mL ÷ mL per week
10 ÷ 0.6 = about 16.7 weeks
If you enter a dose per injection instead, step 1 runs the other way: weekly mg = mg per injection × injections per week.
Terms used on this page
- Milligram (mg)
- A unit of weight. One milligram is one thousandth of a gram.
- Milliliter (mL)
- A unit of liquid volume. One milliliter is one thousandth of a liter.
- Concentration (mg/mL)
- How many milligrams of testosterone are in each milliliter of liquid. It is printed on the vial label.
- Syringe unit
- A mark on an insulin syringe. On a U-100 syringe, 100 units equal 1 mL, so 1 unit is 0.01 mL.
Common questions
Does this calculator tell me what dose to take?
No. It only converts the dose your prescriber set into mL and syringe units. It does not know your health, your lab results or your goals, so it cannot pick a dose, a schedule or a product.
What does U-100 mean on an insulin syringe?
U-100 means the syringe is marked for 100 units in each mL. So 1 unit is 0.01 mL, 10 units is 0.1 mL and 50 units is 0.5 mL. These units are volume marks only. They are not milligrams of testosterone.
Why does the vial strength change the volume?
A 200 mg/mL vial has twice as much testosterone in each mL as a 100 mg/mL vial. So the same mg dose takes half the volume from the stronger vial. Always use the strength printed on your own vial.
How long can I keep using a vial after opening it?
That limit comes from your vial's label or your pharmacist, not from math. The calculator only shows how many weeks of injections the liquid in the vial covers.
Sources
The math is plain unit conversion. The notes on this page draw on these sources.
- Usach I, Martinez R, Festini T, Peris JE. Subcutaneous injection of drugs: literature review of factors influencing pain sensation at the injection site. Adv Ther 2019;36:2986-2996.About 1.5 mL is the volume generally accepted for one injection under the skin.
- Oxford Health NHS Foundation Trust. Guidance on the administration of intramuscular injections in in-patient settings (2024).Lists different maximum volumes for different muscles.
- DEPO-Testosterone (testosterone cypionate injection), US prescribing information. DailyMed.Supplied as 100 and 200 mg/mL in 10 mL vials. The example values stay inside its labelled range.
- Bhasin S, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2018;103:1715-1744.Its typical starting doses (75 to 100 mg per week, or 150 to 200 mg every 2 weeks) fall inside the example range on this page.