Free Peptide Calculator (+ Guide)

What is a peptide calculator?

A peptide calculator turns a dose in micrograms or milligrams into the units to draw on an insulin syringe, once the powder in the vial is mixed with water.

This one also shows the strength of the mix, the doses in the vial and how long it lasts.

How it works

The calculator works it out on your device, and your numbers stay there.

The peptide reconstitution math

Three steps take you from the label to the line on the syringe.

1,000 mcg is 1 mg, so a 250 mcg dose is 0.25 mg.

Reading a U-100 syringe

An insulin syringe marked U-100 holds 100 units in each mL, as the FDA's clearance for one puts it. The units are lines on the barrel, so the same line holds more or less peptide depending on the mix.

Sizes differ in how finely they're marked. BD's own filing with the FDA lists the lines.

A small dose is easier to draw on a small syringe. The calculator shows when your dose falls between two lines, and how far the nearest one is.

Units are not milligrams

In July 2024 the FDA warned of overdoses with compounded semaglutide, some needing hospital care. Confusion between milliliters, milligrams and units may have contributed, it said.

It asked providers to give patients the right syringe size for the dose and show them how to measure it. That's the step this calculator draws.

Choosing how much water to add

More water makes a weaker mix, so the same dose takes more units. Less water makes a stronger mix and fewer units.

The table under the result shows your dose at 0.5 to 3 mL of water. A ✓ marks the amounts where it lands right on a line.

Or switch to "The units I want", pick 10 units, and it finds the water for you.

A worked example

Here's the example the calculator loads: a 5 mg vial with 2 mL of water, a 250 mcg dose, seven times a week, on a 1 mL syringe.

The mix is 2.5 mg/mL, so each unit holds 25 mcg. The dose is 0.1 mL, which is 10 units, right on a line.

The vial holds 20 doses, which last 20 days at seven a week.

What the FDA says about compounded peptides

Compounded drugs don't go through the FDA's premarket review for safety, quality or effectiveness, the semaglutide alert notes.

The FDA also lists bulk substances that may present significant safety risks. BPC-157 was in that list before its nomination was withdrawn, and the FDA says it lacks the information to know whether it would harm people.

Mistakes to avoid

These are the slips that come up most.

• Reading units on the syringe as milligrams or micrograms
• Mixing up mcg and mg, which moves the dose 1,000 times
• Using a different amount of water than the one you typed
• Drawing a tiny dose on a 1 mL syringe, where each line is 2 units

Who is the peptide calculator for?

It's for people who mix a vial on a prescription and want to check the math before they draw, and these tools help around it.

• Protein calculator – for the protein a day you need
• Calorie calculator – for a calorie target
• BMI calculator – for your BMI and its band
• Water intake calculator – for a day's water

Check the units with your pharmacist the first time, and keep the drawing as your guide.