How to Calculate Peptide Doses: Step by Step

The Three Core Formulas for Peptide Dosing

Calculating peptide doses requires three simple formulas. Once you understand these, you can determine the correct syringe volume for any peptide at any reconstitution. The Peptide Calculator Plus automates all three calculations, but understanding the math builds confidence and helps catch errors.

Step 1: Calculate Concentration

After reconstituting your peptide vial with bacteriostatic water, the first step is determining the concentration of the resulting solution.

Formula: Concentration (mg/mL) = Vial Strength (mg) / Water Volume (mL)

To convert to mcg/mL: multiply by 1,000.

Examples

• 5 mg BPC-157 + 2 mL BAC water = 2.5 mg/mL = 2,500 mcg/mL
• 10 mg Melanotan II + 2 mL BAC water = 5 mg/mL = 5,000 mcg/mL
• 2 mg CJC-1295 + 2 mL BAC water = 1 mg/mL = 1,000 mcg/mL
• 5 mg Semaglutide + 3 mL BAC water = 1.667 mg/mL

Step 2: Calculate Volume to Draw

Once you know the concentration, calculate how much liquid to draw for your desired dose.

Formula: Volume (mL) = Desired Dose / Concentration

Make sure dose and concentration use the same unit (both mg or both mcg).

Examples

• 250 mcg BPC-157 from 2,500 mcg/mL = 0.1 mL
• 500 mcg Melanotan II from 5,000 mcg/mL = 0.1 mL
• 100 mcg CJC-1295 from 1,000 mcg/mL = 0.1 mL
• 0.5 mg Semaglutide from 1.667 mg/mL = 0.3 mL

Step 3: Convert Volume to Syringe Units

U-100 insulin syringes mark 100 units per 1 mL. The conversion is straightforward:

Formula: Syringe Units = Volume (mL) x 100

Examples

• 0.1 mL = 10 units
• 0.05 mL = 5 units
• 0.25 mL = 25 units
• 0.3 mL = 30 units

Complete Worked Example: BPC-157

Let us walk through a complete calculation for a common BPC-157 protocol:

1. Vial: 5 mg BPC-157
2. Reconstitution: Add 2 mL bacteriostatic water
3. Concentration: 5 mg / 2 mL = 2.5 mg/mL = 2,500 mcg/mL
4. Desired dose: 250 mcg
5. Volume: 250 mcg / 2,500 mcg/mL = 0.1 mL
6. Syringe units: 0.1 mL x 100 = 10 units
7. Doses per vial: 5,000 mcg / 250 mcg = 20 doses

You would draw to the 10-unit mark on your U-100 insulin syringe, and the vial would last 20 injections at this dose.

Bonus Formula: Doses Per Vial

Formula: Doses Per Vial = Total Peptide (mcg or mg) / Dose Per Injection (same unit)

This tells you how many injections you can get from one vial, which is essential for planning purchases and protocol length.

Common Mistakes to Avoid

• Mixing up mg and mcg -- This is the number one error. Always double-check your units. A 250 mg dose is 1,000x larger than 250 mcg.
• Using the wrong syringe -- U-100 syringes have 100 units per mL. U-40 syringes (used for some insulin types) have 40 units per mL. Using a U-40 syringe with U-100 calculations will give the wrong dose.
• Forgetting to account for dead space -- Insulin syringes have a small amount of dead space in the needle hub. For very small doses (under 5 units), this can affect accuracy. Using a larger reconstitution volume increases the volume per dose, reducing the impact of dead space error.
• Not accounting for reconstitution water in the volume -- When you add water to the vial, the final volume equals the water added plus the peptide volume (which is negligible for small peptide amounts). For practical purposes, the final volume equals the water added.

Why Use the Peptide Calculator Plus?

While the math is simple, the Peptide Calculator Plus eliminates errors by handling unit conversions automatically, showing visual syringe fill levels, providing preset values for 30+ peptides, calculating doses per vial and total protocol cost, and working offline with no data sent to servers. The calculator is free, requires no account, and gives you instant results for any peptide at any reconstitution volume.