Injection volume calculator
For ready-made vials labelled in mg/mL, like testosterone at 200 or 250 mg/mL. Everything is worked out in your browser.
Volume = amount ÷ strength. A 250 mg/mL oil holds 25 mg in every 0.1 mL. Under 1 mL it can be drawn on a 1 mL insulin syringe, where 0.1 mL is the 10 mark.
Every 3.5 days is 2 injections a week; every other day is 3.5.
For planning only. Check every dose against your prescription.
Questions
How do I convert mg to mL?
Divide the amount in mg by the strength of the vial in mg/mL, which is printed on the label. A 200 mg/mL vial holds 20 mg in every 0.1 mL, so the volume grows in step with the amount. The calculator does this for any strength.
How many units is that on an insulin syringe?
A U-100 insulin syringe has 100 units per mL, so each unit is 0.01 mL. Multiply the volume in mL by 100: 0.5 mL is the 50 mark. Oil-based products are often drawn with a larger needle and then swapped, so check the syringe you've been given.
How long will my vial last?
Multiply the strength by the vial size to get the total in the vial, then divide by the amount you use each week. Real vials give a little less than the maths, because some is left in the needle and the bottom of the vial each time.
Does splitting a weekly amount change how long the vial lasts?
No. The weekly total is the same whether it's one injection or several, so the vial lasts the same time. Splitting changes the peaks and dips in your levels, which the half-life calculator shows.
What if a lab test shows my vial isn't the strength on the label?
Enter the tested strength instead of the label strength to see the volume that actually contains the amount you've been prescribed. Our guide on lab-tested vials explains what to do with doses you've already logged.