Choose what you already know
Start with either your prescribed weekly target in mg or the mL you use for each injection.
How TRT Dose Calculator Works
Enter your prescribed target, vial concentration, and injection frequency to calculate the volume and U-100 units for each injection.
Short answer
What does the TRT calculator do?
It converts a weekly target in mg into the amount to draw for each injection. You can also enter the dose in mg for each injection to calculate the corresponding volume and weekly total. The result includes mL, mg, U-100 units, a schedule, and estimated vial usage.
Check the vial concentration
Enter the exact mg/mL value printed on your vial label, for example 250 mg/mL.
Select your prescribed frequency
Choose how many injections are scheduled each week. The calculator uses this number to split the weekly target.
Read the amount per injection
The main result shows the calculated mL and the equivalent marking on a U-100 syringe.
The calculation
From weekly mg to mL per injection
In weekly target mode, the calculator first splits the weekly amount by frequency, then converts that dose from mg to mL using the vial concentration.
Weekly target mode
mL per injection = weekly target (mg) ÷ injections per week ÷ concentration (mg/mL)
- mg
- The amount of medication, not the liquid volume.
- mL
- The volume of liquid drawn into the syringe.
- U-100 units
- The syringe scale: 100 units equals 1 mL, so 1 unit equals 0.01 mL.
If you enter the dose per injection in mg, the calculator converts it to mL and shows the average weekly amount.
Worked example
200 mg/week at 250 mg/mL, every day
You enter
- Weekly target
- 200 mg
- Concentration
- 250 mg/mL
- Frequency
- Every day
- Injections per week
- 7
You get
- mg per injection
- ≈28.57 mg
- Exact volume
- ≈0.1142857 mL
- Calculation and schedule precision
- 0.1142857… mL
- Compact result card
- 0.11 mL
- If 0.11 mL is actually used daily
- 192.5 mg/week
- U-100 scale
- ≈11.4 units
- Weekly volume
- 0.8 mL
The calculation is 200 ÷ 7 = 28.5714 mg per injection; 28.5714 ÷ 250 = 0.1142857 mL; 0.1142857 × 100 = 11.4286 U-100 units. The calculator and schedule data use the full internal value; calendar text displays 0.114 mL, while the compact result card displays 0.11 mL. Actually administering 0.11 mL daily at 250 mg/mL equals 27.5 mg per injection and 192.5 mg/week, not 200 mg/week. Display rounding is not a dosing recommendation; practical rounding to syringe markings must be confirmed with a licensed medical professional.
Calculation details
All calculations run locally in the browser. Changing language changes the text, not the numerical precision.
1. Doses per week
doses_per_week = 7 / interval_days
2. mg per injection
mg_per_injection = weekly_mg / doses_per_week
3. mL per injection
mL_per_injection = mg_per_injection / concentration_mg_per_mL
4. Weekly mL
weekly_mL = weekly_mg / concentration_mg_per_mL
5. U-100 units
units_per_injection = mL_per_injection × 100
6. Complete injections from a vial
complete_injections = floor(vial_volume_mL / mL_per_injection)
7. Remaining vial volume
remaining_mL = vial_volume_mL − (complete_injections × mL_per_injection)
8. Estimated days of supply
interval_days = 7 / injections_per_week; days_of_supply = complete_injections × interval_days
Vial usage is an estimate. The implementation counts only complete injections with floor, calculates the volume remaining after them, and multiplies their number by the interval between injections. The interface rounds estimated days to the nearest whole day and displays a remainder of up to 0.01 mL as 0 mL. The estimate does not account for draw loss, dead space, or measurement error.
Precision and limitations
What is the difference between exact and rounded values?
- Exact calculated value
- The calculator retains the full value for subsequent calculations. In the example it is approximately 0.1142857 mL.
- Displayed value
- The card shows a compact 0.11 mL, the detail line shows 0.1143 mL, and the calendar shows 0.114 mL. Calculations and schedule events use the unrounded internal value. Actually administering 0.11 mL daily at 250 mg/mL gives 192.5 mg/week, so display rounding must not be treated as a dose recommendation.
- U-100 units
- U-100 denotes a scale of 100 units per 1 mL, so 1 unit on that scale equals 0.01 mL.
- Not a practical instruction
- The calculator does not determine which marking, syringe, dose, or frequency is appropriate. Verify the label, device, and prescription with a licensed medical professional.
Method and sources
How is the logic checked?
The formulas are direct conversions between mg, mg/mL, and mL. The worked example above can be calculated by hand and serves as a check of the output. The calculator does not interpret laboratory results or suggest treatment.
- DailyMed: official labeling that defines U-100 as 100 units/mL
- CDC: general information on safe injection practices
- Full medical disclaimer and calculator limitations
Methodology last updated: July 30, 2026.
Educational use only · not medical advice. Verify every dose with a licensed clinician. Read the full disclaimer.
