Peptide Dosage Calculator: How to Calculate Your Exact Dose

Written by NorthPeptide Research Team

For laboratory and research use only. Not for human consumption.

Why Accurate Dosing Matters

Getting the math right is the single most important part of working with peptides.

If you add too much water, your solution will be too weak. Too little water, and it is too concentrated. Either way, your measurements will be off — and that means unreliable results.

The good news: the math is simple. Once you understand the basic formula, you can calculate the correct dose for any peptide, any vial size, and any amount of water. This guide will walk you through it step by step.

What You Need Before You Start

Before you do any calculations, make sure you have:

• Your peptide vial — Check the label for the amount (usually listed in milligrams, like “5mg” or “10mg”)
• Bacteriostatic water (BAC water) — The most common solvent for reconstitution. It contains 0.9% benzyl alcohol, which prevents bacteria from growing and keeps your solution usable for 4 to 6 weeks when refrigerated.
• Insulin syringes — Typically marked in “units” (we will explain what that means below)
• Alcohol swabs — For cleaning vial tops before drawing

Important note: Some peptides require acetic acid water instead of BAC water for proper reconstitution. Always check the specific instructions for your peptide before mixing.

The Basic Formula

Here is the only formula you need to remember:

That is it. Once you know the concentration, you can figure out how much liquid to draw for any dose.

Step-by-Step Example

Let us say you have a 5mg vial of BPC-157 and you add 2mL of BAC water.

Step 1: Calculate the concentration.

5mg ÷ 2mL = 2.5 mg/mL

Step 2: Figure out your dose volume.

If your research protocol calls for 250mcg (which is 0.25mg), you need:

0.25mg ÷ 2.5 mg/mL = 0.1mL

Step 3: Convert to syringe units (see next section).

0.1mL = 10 units on a standard insulin syringe.

That is the whole process. Calculate the concentration, divide your desired dose by that concentration, and convert to syringe units.

Understanding Insulin Syringe Units

This is the part that confuses most people. Here is the simple version:

A standard insulin syringe holds 1mL of liquid. It is marked from 0 to 100 in “units.” These units have nothing to do with peptide dosing units — they are just a way to measure tiny volumes of liquid.

So when someone says “draw 10 units,” they mean draw liquid up to the 10 mark on the syringe. That equals 0.1mL.

Think of it like a ruler. The syringe is just a measuring stick for very small amounts of liquid. The “units” are the tick marks.

A Quick Conversion Table

Syringe Units	Milliliters (mL)
5 units	0.05 mL
10 units	0.10 mL
20 units	0.20 mL
25 units	0.25 mL
50 units	0.50 mL
100 units	1.00 mL

Reconstitution Volume Chart

How much water should you add? It depends on the vial size and how concentrated you want the solution. Here is a reference chart showing the concentration you get with different combinations:

Peptide Amount	1mL Water	2mL Water	3mL Water
2mg	2.0 mg/mL	1.0 mg/mL	0.67 mg/mL
5mg	5.0 mg/mL	2.5 mg/mL	1.67 mg/mL
10mg	10.0 mg/mL	5.0 mg/mL	3.33 mg/mL
15mg	15.0 mg/mL	7.5 mg/mL	5.0 mg/mL
30mg	30.0 mg/mL	15.0 mg/mL	10.0 mg/mL

Tip: Adding more water makes it easier to measure small doses accurately, but it also means you need to draw more liquid each time. Adding less water makes the solution more concentrated, which means smaller injection volumes — but mistakes in measurement have a bigger impact. For most peptides, 2mL is a good middle ground.

Quick Reference: Popular Peptide Reconstitution

Here are common reconstitution setups for peptides available at NorthPeptide. These use 2mL of BAC water as the standard volume.

Peptide	Vial Size	BAC Water	Concentration	Solvent Note
BPC-157	5mg	2mL	2.5 mg/mL	BAC water
BPC-157	10mg	2mL	5.0 mg/mL	BAC water
Retatrutide	5mg	2mL	2.5 mg/mL	BAC water
Semaglutide	5mg	2mL	2.5 mg/mL	BAC water
Tirzepatide	10mg	2mL	5.0 mg/mL	BAC water
Sermorelin	5mg	2mL	2.5 mg/mL	BAC water
TB-500	5mg	2mL	2.5 mg/mL	BAC water
GHK-Cu	5mg	2mL	2.5 mg/mL	BAC water

Need BAC water or acetic acid water? You can find both in our shop.

How to Reconstitute: The Actual Process

Now that you understand the math, here is how to physically mix your peptide:

1. Clean everything. Wipe the top of the peptide vial and the BAC water vial with an alcohol swab.
2. Draw the water. Using a syringe, draw your chosen amount of BAC water (for example, 2mL).
3. Add water slowly. Insert the needle into the peptide vial and let the water run down the inside wall of the vial. Do NOT squirt it directly onto the powder — that can damage the peptide.
4. Let it dissolve. Gently swirl the vial. Do not shake it. Most peptides dissolve in 1 to 2 minutes. If it is not dissolving, let it sit in the fridge for a few minutes and try again.
5. Store properly. Once reconstituted, store the vial in the refrigerator (2-8°C). Most reconstituted peptides stay stable for 4 to 6 weeks when refrigerated with BAC water.

Research has shown that bacteriostatic water’s benzyl alcohol preservative is critical for maintaining solution sterility during multi-use access over this storage period.

Common Mistakes to Avoid

Even experienced researchers make these errors. Do not let them trip you up:

• Mixing up mg and mcg. 1mg = 1,000mcg. This is the most common math error. Double-check your unit conversions every time.
• Squirting water directly onto the powder. The force can denature (damage) the peptide. Always let the water trickle down the glass wall.
• Shaking the vial. Shaking creates air bubbles and can damage peptide bonds. Gentle swirling only.
• Using sterile water instead of BAC water. Sterile water has no preservative. Once you puncture the vial, bacteria can grow. BAC water prevents this. (Sterile water is fine for single-use applications, but BAC water is better for multi-draw vials.)
• Storing at room temperature. Reconstituted peptides degrade quickly at room temperature. Refrigerate immediately after mixing.
• Forgetting to note the date. Write the reconstitution date on the vial. After 4 to 6 weeks, the peptide may have degraded even with BAC water.

A Complete Worked Example

Let us put it all together with a real scenario:

How Many Doses Per Vial?

To figure out how long a vial will last, divide the total peptide amount by your dose:

Total peptide (mg) ÷ Dose per use (mg) = Number of doses

For example, a 5mg vial at 250mcg (0.25mg) per dose gives you 20 doses. A 10mg vial at the same dose gives you 40 doses.

This is useful for planning your research timeline and knowing when you will need to reorder.

Summary of Key Research References

Topic	Reference	PMC ID
Peptide storage conditions — comparative study	Kingsmore et al., Journal of Proteomics	PMC3630641
Peptide handling for mass spectrometry assays	Hoofnagle et al., Clinical Chemistry	PMC4830481
Overcoming protein and peptide instability	Banskota et al., Advanced Drug Delivery Reviews, 2023	PMC10526705
HPLC analysis and purification of peptides	Rabel & Bhatt, Methods in Molecular Biology	PMC7119934
Therapeutic peptides — current applications and future directions	Wang et al., Signal Transduction and Targeted Therapy, 2022	PMC8844085

For laboratory and research use only. Not for human consumption. This article is intended for informational purposes and does not constitute medical advice. Always follow your specific research protocol and consult applicable regulations.