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Vial Longevity Calculator

A vial strength divided by a dose gives the number of doses it holds; a frequency turns that into days. A part dose left at the end is reported rather than rounded away — whether it is usable is a fact about the vial, not about the arithmetic.

Last reviewed: September 21, 2026

A vial strength divided by a dose gives the number of doses it holds; a frequency turns that into days.

Optional. Fill this to also read each dose on a syringe.

How the arithmetic works

  • Doses in the vial = vial strength (mg) ÷ dose (mg)
  • Weeks the vial lasts = doses in the vial ÷ doses per week
  • Days the vial lasts = weeks × 7

Both the dose size and the frequency are numbers you supply — this page does not set either. When a vial strength and water volume are both filled in, each dose is also shown as a unit reading on a U-100 syringe.

Worked examples

A 10 mg vial at a 2.5 mg dose, once weekly:

Doses in the vial10 mg ÷ 2.5 mg = 4
At that frequency4 doses ÷ 1/week = 4 weeks (28 days)
Each dose, at 2 mL water5 mg/mL concentration — 50 units

A 10 mg vial at a 3 mg dose, once weekly — a case where the dose doesn’t divide evenly:

Doses in the vial10 mg ÷ 3 mg = 3.33 — 3 whole doses, 1 mg left over
At that frequency3.33 doses ÷ 1/week = 3.33 weeks (23.3 days)

Enter either set of numbers into the calculator above and it returns the same figures.

What changes the answer

  • Dose size. A smaller dose divides into more doses per vial and stretches it further; a larger dose does the reverse.
  • Frequency. More doses per week uses the same vial faster in calendar time, without changing how many doses it holds.
  • Water volume. Only changes the syringe reading for each dose — not the number of doses or how long the vial lasts, which are set by mass alone.

FAQ

How many doses are in a 10 mg vial?
The vial's total mg divided by the dose size. A 10 mg vial at a 2.5 mg dose holds exactly 4 doses. At a 3 mg dose it holds 3.33 doses — 3 whole doses plus 1 mg left over, since 3 mg does not divide evenly into 10 mg.
How long does a vial last?
The number of doses in the vial divided by how many doses are taken per week, expressed in weeks and days. A 10 mg vial at 2.5 mg once weekly holds 4 doses and lasts 4 weeks (28 days) at that frequency. A different frequency changes the answer — the same vial at twice weekly would hold the same 4 doses but last half as long.
vial longevity calculator peptide
This page's calculator takes a vial strength, a dose size, and how many doses are taken per week, and returns how many doses the vial holds and how long that lasts in days and weeks. Adding a water volume also reads each dose on a U-100 syringe.
What happens to the leftover amount when doses don't divide evenly?
It's reported, not discarded by the arithmetic. A 10 mg vial at 3 mg a dose yields 3 whole doses with 1 mg remaining — whether that remainder is usable is a question about the physical vial (residual volume, whether it can still be drawn accurately) that this page does not answer.
Does the water volume affect how many doses are in a vial?
No. The number of doses in a vial is set by mass alone — the vial's total mg divided by the dose in mg — and does not depend on how much water it was reconstituted with. Water volume determines the concentration, which is why it's an optional field here: fill it in and each dose also reads on a syringe.

To divide a single dose across more than one administration instead, see the split dose calculator. For a specific compound’s own vial sizes, see the general peptide dosage calculator.