How many doses are in a 5 mg vial?

It depends only on the dose size, not on how much diluent you added. A 5 mg vial holds 5000 mcg, so at 250 mcg per dose that is 20 doses and at 500 mcg it is 10. The bacteriostatic water changes the volume you draw, never the number of doses.

Why do I get fewer doses than the calculator says?

Because liquid is left behind. A syringe hub and needle retain a small volume after the plunger bottoms out, and a little always stays in the vial that cannot be drawn. Over many draws that adds up, so the last dose is often short. Treat the figure as the ceiling.

Does adding more water give me more doses?

No. The amount of peptide in the vial is fixed the moment it is manufactured. More diluent spreads the same peptide through more liquid, so you draw more volume for the same dose and finish at the same time.

Doses Per Vial Calculator

Doses in the vial

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Enter the vial size and your dose.

That covers: –
Total peptide: –

The working

This works out the arithmetic for the figures you enter. It does not recommend doses and does not know what is in your vial.

The diluent has nothing to do with it

doses = vial (mcg) ÷ dose (mcg)

The peptide in the vial is fixed. Adding more bacteriostatic water spreads it through more liquid, which makes each dose a larger volume, and that is the whole of the effect. The number of doses is the dry weight divided by the dose size, and no reconstitution choice moves it.

This is worth stating because it is the most common misconception in the niche. If a thinner mix seems to last longer, it is because the doses were smaller, not because the water did anything.

Doses in a vial at common sizes

Vial	Dose	Doses
5 mg	250 mcg	20
5 mg	500 mcg	10
10 mg	250 mcg	40
10 mg	500 mcg	20
15 mg	500 mcg	30
20 mg	1000 mcg	20

Why the real number is lower

Every calculator in this niche prints the division and stops, which quietly overstates what you get. Two things eat into it.

Syringe dead space. The hub and needle hold a small volume after the plunger has bottomed out, and it does not get injected. It is small per dose and it happens every dose.

What stays in the vial. The last fraction of a millilitre cannot be drawn cleanly, particularly once the needle can no longer reach it at an angle. A thinner reconstitution makes this worse in absolute terms, because the same residual volume carries more of your peptide when the solution is more dilute.

So treat the figure above as a ceiling rather than a count. If the last dose comes up short, nothing has gone wrong. The main calculator gives the same figure alongside the draw, and how much water to add covers the dilution trade.

Questions

How many doses are in a 5 mg vial?: It depends only on the dose size, not on how much diluent you added. A 5 mg vial holds 5000 mcg, so at 250 mcg per dose that is 20 doses and at 500 mcg it is 10. The bacteriostatic water changes the volume you draw, never the number of doses.
Why do I get fewer doses than the calculator says?: Because liquid is left behind. A syringe hub and needle retain a small volume after the plunger bottoms out, and a little always stays in the vial that cannot be drawn. Over many draws that adds up, so the last dose is often short. Treat the figure as the ceiling.
Does adding more water give me more doses?: No. The amount of peptide in the vial is fixed the moment it is manufactured. More diluent spreads the same peptide through more liquid, so you draw more volume for the same dose and finish at the same time.