Last updated: May 2026
Testosterone Injection Calculator
Quick answer: A 100 mg weekly dose from a 200 mg/mL vial is 100 ÷ 200 = 0.50 mL, which sits at the 50-unit mark on a U-100 insulin syringe. Formula: Volume (mL) = Dose (mg) ÷ Concentration (mg/mL).
About this calculator
This testosterone dose calculator — also called a testosterone dosage or TRT injection calculator — converts a prescribed testosterone dose into the exact volume to draw from a vial using the formula Volume (mL) = Dose (mg) ÷ Concentration (mg/mL). It is built for people managing an active TRT protocol — enter your vial concentration and prescribed dose to get your draw volume instantly. Supports weekly, every-N-days, and mL-to-mg modes. Free, instant, no login.
On a very low or sub-therapeutic dose? If you're following a women's low-dose protocol, use the dedicated women's low-dose testosterone microdosing calculator — it supports dose increments down to 0.5 mg/week and the small draw volumes those protocols need.
How to use this calculator
You need three pieces of information from your prescription and vial label: the vial concentration (mg/mL), your prescribed dose (mg), and how often you inject.
Select your mode — Weekly dose if your doctor gave you a weekly amount, Every N days if you inject on a fixed interval, or mL to mg if you want to verify what a drawn volume corresponds to in milligrams.
Enter your values and the result updates immediately. The calculator also shows syringe fill level so you can cross-check what you see in the barrel.
Worked example
Example — weekly injection
Vial concentration: 200 mg/mL (testosterone cypionate)
Prescribed weekly dose: 100 mg
Injection frequency: once per week
Draw = 100 ÷ 200 = 0.50 mL
Example — twice-weekly (every 3.5 days)
Vial concentration: 200 mg/mL
Prescribed weekly dose: 160 mg
Interval: 3.5 days (twice per week)
Per-injection dose = 80 mg → Draw = 80 ÷ 200 = 0.40 mL
How to interpret your result
The result is the volume in mL to draw from your vial for each injection. On a standard 1mL (U-100) insulin syringe, 0.5mL corresponds to the 50-unit mark. On a 3mL syringe, 0.5mL is at the 0.5 mark on the barrel.
Always verify the drawn volume against the syringe markings before injecting. The calculator is a maths tool — always confirm dosing with your prescribing doctor or pharmacist.
Common vial concentrations
| Concentration | 100 mg dose | 150 mg dose | 200 mg dose |
|---|
| 100 mg/mL | 1.00 mL | 1.50 mL | 2.00 mL |
| 200 mg/mL | 0.50 mL | 0.75 mL | 1.00 mL |
| 250 mg/mL | 0.40 mL | 0.60 mL | 0.80 mL |
Choosing the right syringe for TRT
Once you know your draw volume, the syringe you use determines how accurately you can measure it. Most TRT injections fall between 0.25 mL and 1 mL. A 1 mL (U-100) insulin syringe is graduated in single units (0.01 mL), which makes small or fractional volumes easy to read — well suited to subcutaneous and shallow intramuscular injections. A 3 mL syringe holds more and is often used when drawing from a multi-dose vial, but its wider barrel makes very small volumes harder to measure precisely.
Many people draw the dose with one needle and switch to a fresh, finer needle to inject. Needle gauge and length depend on your injection site and body composition, not on the calculator's output — the best injection sites for TRT guide covers site selection, and TRT protocols explained shows how injection frequency affects the volume per shot. Always confirm your technique and equipment with your prescriber or pharmacist.
Frequently asked questions
How do I calculate my TRT injection volume?
Divide your prescribed dose (mg) by your vial concentration (mg/mL): Volume (mL) = Dose ÷ Concentration. A 100 mg dose from a 200 mg/mL vial is 100 ÷ 200 = 0.50 mL per injection. The calculator above does this instantly and also shows the fill level on the syringe barrel so you can cross-check.
What is vial concentration?
Vial concentration is the strength of your testosterone preparation, expressed in mg per mL. Common values are 100 mg/mL and 200 mg/mL. It is printed on the vial label — look for the format "200 mg/mL" or "200 mg/1mL".
What is the formula the calculator uses?
Volume (mL) = Dose (mg) ÷ Concentration (mg/mL). This is standard pharmaceutical dilution maths. The calculator applies this formula exactly — no adjustments or estimations.
How many mg of testosterone is in 1 mL?
It depends on your vial's concentration, which is printed on the label in mg/mL. One millilitre of a 100 mg/mL preparation contains 100 mg; 1 mL of a 200 mg/mL preparation contains 200 mg. To find the milligrams in any volume, multiply the volume (mL) by the concentration (mg/mL). Select your concentration in the calculator above and use mL → mg mode to check any volume.
How much testosterone is in 0.5 mL?
That depends entirely on your vial's concentration. At 100 mg/mL, 0.5 mL is 50 mg; at 200 mg/mL, 0.5 mL is 100 mg; at 250 mg/mL it is 125 mg. If your prescription is written as a volume in mL and you want the milligram equivalent, switch the calculator to mL → mg mode and enter 0.5 mL with your concentration.
How do I convert the mL my doctor wrote into mg?
Use the calculator's mL → mg mode. Enter the volume your prescriber wrote (for example 0.4 mL) and your vial concentration, and it returns the dose in milligrams (0.4 mL × 200 mg/mL = 80 mg). This is useful when a prescription is given as "draw to 0.4 mL" rather than as a milligram dose.
What if I inject every 3.5 days?
Use the "Every N days" mode. Enter 3.5 as your interval and your total weekly prescribed dose. The calculator splits the weekly dose proportionally (weekly dose ÷ 7 × interval) and returns the volume per injection.
Can I split my weekly testosterone dose into two injections?
Yes — many protocols split a weekly dose into two or more smaller injections to keep levels steadier. Select "Every N days" mode, enter your total weekly dose and your interval (for example 3.5 days for twice weekly), and the calculator returns the per-injection volume. Whether to split your dose, and how often, is a decision for your prescriber — our
TRT protocols guide compares weekly, E3D and EOD schedules.
Can I use this for testosterone enanthate, cypionate, or propionate?
Yes. The calculator works for any oil-based testosterone ester. The only inputs that matter are the concentration on your specific vial label and your prescribed dose — the ester type does not change the maths.
What size syringe do I need for a TRT injection?
Most TRT injection volumes fall between about 0.25 mL and 1 mL. A 1 mL (U-100) insulin syringe makes small volumes easy to measure precisely and suits subcutaneous or shallow intramuscular injections; a 3 mL syringe is often used for drawing from a multi-dose vial. Many people draw with one needle and inject with a fresh, finer one. Needle gauge and length depend on your injection site and body composition — see our
injection sites guide for a full breakdown.
Does subcutaneous vs intramuscular injection change the dose or volume?
No. The volume to draw is determined only by your prescribed dose and your vial concentration, so the maths is identical whether you inject subcutaneously or intramuscularly. The injection route can affect absorption and is a clinical choice to make with your prescriber, but it does not change the number this calculator gives you.
My result shows 0.08 mL — how do I measure that accurately on my syringe?
A volume of 0.08 mL equals 8 units on a U-100 insulin syringe. Standard 0.3 mL syringes (30-unit capacity) have 1-unit graduation marks, so 8 units is visible and measurable. For very small draws, pull the plunger slowly past your mark then push back to the exact line — this clears air from the needle tip and gives a more accurate read. If you consistently draw under 0.10 mL, ask your pharmacy whether a lower-concentration vial (e.g., 100 mg/mL instead of 200 mg/mL) is available — halving the concentration doubles your draw volume for the same dose, making it easier to measure precisely.
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How this is calculated
This calculator divides your prescribed dose by the vial concentration to find the injection volume, then converts that volume to insulin-syringe units (volume in mL × 100 for a U-100 syringe). It is arithmetic only — nothing you enter is stored or sent anywhere, and the result is not medical advice. Always confirm your dose with your prescriber.