Free tool

Vial duration calculator

Work out how many full doses a vial holds, how many weeks it will last at your dose and frequency, and (optionally) what each dose costs. Works for any compound measured in milligrams.

Reviewed for accuracy · Last reviewed July 8, 2026
Vial size
mg
Dose per injection
mg
Injections per week
/ week
Vial price (optional)
$
Your vial lasts4 weeks4 full doses of 2.5 mg

How the math works

Doses per vial is the vial size divided by the dose, rounded down to full doses: a 10 mg vial at 2.5 mg per injection holds 4 doses, and any remainder smaller than a full dose is left out. Weeks per vial is doses divided by injections per week. Cost per dose is the vial price divided by the doses it holds, and the monthly figure assumes an average month of about 4.35 weeks.

One practical limit to keep in mind: a reconstituted vial does not keep forever. Mixes with bacteriostatic water are commonly used within about 28 days refrigerated, so a vial that lasts longer than a month on paper may hit its use window first. To get the concentration and syringe draw for your mix, use the reconstitution calculator. If your dose is still stepping up, the titration schedule planner shows when it changes, which also changes how long each vial lasts.

FAQ

How long does a 10 mg vial of tirzepatide last?Divide the vial by the dose. At 2.5 mg once weekly, a 10 mg vial holds 4 full doses and lasts 4 weeks. At 5 mg weekly it holds 2 doses and lasts 2 weeks. Partial leftovers smaller than a full dose are not counted.
How many doses are in a 5 mg vial?Vial size divided by dose, rounded down. A 5 mg vial holds 20 doses at 0.25 mg, 10 doses at 0.5 mg, or 2 doses at 2.5 mg. The calculator above does this for any combination.
Will the vial expire before I finish it?Possibly. Peptides reconstituted with bacteriostatic water are commonly used within about 28 days refrigerated, and some product labels specify shorter windows. If the calculator says a vial lasts longer than that, the practical limit is the use window, not the milligrams.
How do I work out cost per dose?Divide the vial price by the number of full doses it holds. A $200 vial that holds 4 doses is $50 per dose. Enter a price in the calculator to see cost per dose and an estimated monthly cost.
Tracking doses from a shared vial? PepHub can log each draw and show what is left.Learn more →

This tool is an independent educational reference and is not medical advice. Talk to a doctor before starting or adjusting any compound.