Peptide Dose Calculator: Reconstitution, Injection Volume, and Vial Math

If you’ve ever stared at a vial and a syringe trying to remember the formula, this post is for you. Peptide dose math is the same calculation every time—but it’s just tedious enough that most people look it up again each time they do it.

Here’s the math explained clearly, and a breakdown of the three calculations you’ll run most often.

What You’re Actually Solving For

When you reconstitute a peptide from powder, you have a vial of lyophilized compound and a vial of bacteriostatic water (BAC water). You need to figure out:

How much BAC water to add – this sets your concentration
How many units to draw per dose – this is your injection volume
How many doses you’ll get from the vial – so you know when to reorder

These three calculations are connected. Get the concentration right and the rest follows.

Calculation 1: Reconstitution (Setting Your Concentration)

What you know:

Vial size: the amount of peptide in the vial, in milligrams (mg) or micrograms (mcg)
Target concentration: how potent you want each mL to be

The formula:

BAC water to add (mL) = Vial size (mg) / Target concentration (mg/mL)

Example:

You have a 5 mg vial of BPC-157
You want a concentration of 2 mg/mL
BAC water to add: 5 / 2 = 2.5 mL

Now every mL of solution contains 2 mg of peptide.

A few things to keep in mind:

Most people use 1 mL to 2.5 mL of BAC water per 5 mg vial, depending on the peptide and their dosing preference. More BAC water = lower concentration = larger injection volume per dose.
The amount of BAC water does not affect how much peptide you’re getting–just how concentrated the solution is.
Use bacteriostatic water, not sterile water, if you’re reconstituting for multiple doses. BAC water contains benzyl alcohol as a preservative.

Calculation 2: Injection Volume (How Much to Draw Per Dose)

What you know:

Your target dose (in mcg or mg)
Your concentration (from calculation 1, in mg/mL)
Your syringe: standard insulin syringes are 100 units per mL

The formula:

Draw volume (units) = (Target dose / Concentration) x 100

Example:

Target dose: 250 mcg (0.25 mg) of BPC-157
Concentration: 2 mg/mL
Draw volume: (0.25 / 2) x 100 = 12.5 units

So you’d draw to the 12.5-unit mark on your insulin syringe.

If you’re working in mcg: convert your concentration to mcg/mL first (multiply mg/mL by 1000), then apply the same formula. You get the same answer either way.

Calculation 3: Doses Per Vial

What you know:

Total amount of peptide in the vial (mg)
Your dose per injection (mg or mcg)

The formula:

Doses per vial = Vial size / Dose per injection

Example:

Vial: 5 mg
Dose per injection: 0.25 mg (250 mcg)
Doses per vial: 5 / 0.25 = 20 doses

This tells you exactly when you need to reorder–and it’s useful when comparing cost across different vial sizes.

Why This Math Goes Wrong

The most common errors in peptide dosing math:

Unit confusion. Mixing mg and mcg mid-calculation is the biggest source of errors. Pick a unit and stay in it the whole way through. (1 mg = 1000 mcg)

Forgetting syringe scale. Insulin syringes are calibrated in units, where 100 units = 1 mL. If your math gives you a volume in mL, multiply by 100 to get your syringe mark.

Recalculating after every reconstitution. If you change your BAC water amount, your concentration changes and your draw volume changes. A new reconstitution should trigger a recalculation.

Estimating instead of calculating. “About a quarter of the way up” is not a dose. Small peptide doses can be significantly off from even a small drawing error.

How TrackMe+’s Dose Calculator Works

TrackMe+ has a built-in dose calculator with three modes:

Injection tab: Enter your concentration and target dose. It calculates your draw volume in units. This is the one you’ll use every time you dose.

Reconstitution tab: Enter your vial size and how much BAC water you plan to add. It shows you the resulting concentration and draw volume for your target dose. Useful when setting up a fresh vial.

Convert tab: Convert between common units (mg to mcg, mL to units) without reaching for a separate calculator.

The math is the same as doing it by hand–it’s just faster, and the history of what you entered stays attached to that medication in your log.

Tracking Beyond the Math

Once you’ve got the dose right, the next useful thing is tracking whether you’re actually taking it consistently.

TrackMe+ logs every dose you record: date, time, and amount. The calendar view shows your actual dosing pattern over time, not just your intended schedule. The adherence report compares expected vs. completed doses and gives you a compliance percentage.

For protocols with cycles–on periods, off periods, repeat–the app tracks where you are in the cycle so you’re not counting days manually.

Single-use depletion mode tracks how many doses remain as you work through a vial. When you’re down to the last few doses, you know it.

All of it free. trackmeplus.com

Summary: The Three Numbers You Need

What to Calculate	Formula	Example
BAC water to add	Vial size (mg) / Target concentration (mg/mL)	5 mg / 2 mg/mL = 2.5 mL
Draw volume (units)	(Dose / Concentration) x 100	(0.25 / 2) x 100 = 12.5 units
Doses per vial	Vial size / Dose per injection	5 mg / 0.25 mg = 20 doses

Do the reconstitution calculation once when you set up a vial. Do the injection volume calculation before each dose if anything has changed. Know your doses-per-vial so you’re not caught short.

TrackMe+ tracks medications, labs, blood pressure, and weight in one free app. Dose calculator included for peptide and compound users. trackmeplus.com