How do I calculate my TRT injection volume?

Divide your prescribed dose in mg by your vial concentration in mg/mL. A 100mg dose from a 200mg/mL vial equals 0.5mL per injection. The calculator does this automatically.

What is vial concentration in the TRT calculator?

Vial concentration is the strength of your testosterone preparation, expressed in mg/mL. Common values are 100mg/mL and 200mg/mL (also written as 100mg/1mL or 200mg/1mL). It is printed on your vial label.

What if I inject every 3.5 days instead of weekly?

Use the 'Every N days' mode in the TRT calculator. Enter 3.5 as your interval and your total weekly dose. The calculator will divide the dose proportionally and return the volume per injection.

Testosterone Injection Calculator — TRT Dosage & Volume

Last updated: May 2026

About this calculator

The TRT dose 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.

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

Frequently asked questions

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.

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 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.

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.