Arithmetic. Put in a vial size, a reconstitution volume, an amount per draw and what you paid, and it tells you draws per vial, syringe units per draw, how many weeks the vial lasts at a given pace, and cost per week. It doesn't know you and it recommends nothing.
Want it on your phone? The same calculator is at Vial Tool as an installable app that works offline. Compound charts: tirzepatide, semaglutide, GHK-Cu, BPC-157.
How the math works
Reconstitution is just dilution. Milligrams in the vial divided by millilitres of water gives concentration in mg per mL. An amount in micrograms divided by that concentration gives the volume of one draw, and on a standard insulin syringe 1 mL is 100 units, so volume × 100 is units. Draws per vial is milligrams × 1000 ÷ micrograms per draw, rounded down. Cost per draw is what you paid divided by that.
Two things the calculator can't tell you: whether a given draw volume is practical on your syringe (it warns if it's over a full syringe, that's all), and anything at all about whether any of this is a good idea for you. That's what the doctor questions are for.
The mistakes I see most
- Confusing mg and mcg. A thousand micrograms is one milligram. Most vials are labelled in mg; most draw amounts get discussed in mcg. Check which one you're typing.
- Forgetting the water. Concentration changes with how much you add. Two vials of the same size reconstituted differently give different units per draw.
- Reading units as amount. Units on an insulin syringe measure volume, not compound. Ten units of a 2.5 mg/mL solution and ten units of a 5 mg/mL solution are different things.
- Ignoring what a week actually costs. That's what the bottom row is for, and it's usually the number that ends the 'clinic vs research-grade' conversation.