How This Calculator Works
Enter three values: the total peptide in your vial (mg), the amount of bacteriostatic water you add (mL), and your target dose (mcg). The calculator shows the exact number of insulin syringe units to draw, with a visual syringe reference so you can see the fill line before you ever touch the plunger.
Common Presets
Total peptide in the vial before mixing
Amount of BAC water added to the vial
The dose you want per injection
Step-by-Step Breakdown
Step A: Convert mg to mcg
5 mg x 1,000 = 5,000 mcg
Step B: Calculate Concentration
5,000 mcg / 2 mL = 2,500 mcg/mL
Step C: Calculate Draw Volume
250 mcg / 2,500 mcg/mL = 0.1000 mL
Step D: Convert to Syringe Units
0.1000 mL x 100 = 10.0 units
Draw This Amount
10 units
(0.10 mL) on a U-100 insulin syringe
This vial provides approximately 20 doses at 250 mcg each
Visual Reference
U-100 Insulin Syringe
Disclaimer: This calculator is for educational and informational purposes only. Always verify calculations with your prescribing physician or pharmacist before administering any injection. Rounding to the nearest 0.5 unit reflects the smallest graduation on most insulin syringes.
Why Reconstitution Math Matters
Peptide reconstitution is the process of dissolving lyophilized (freeze-dried) peptide powder into a liquid form suitable for injection. The amount of bacteriostatic water you add directly determines the concentration of your solution, which in turn determines how many units you need to draw for an accurate dose.
Getting this math wrong is one of the most common mistakes in self-administered peptide therapy. Too much water makes the solution too dilute, requiring large injection volumes that cause more injection-site irritation. Too little water creates a highly concentrated solution where tiny measurement errors can mean significant dosing inaccuracies. The goal is to hit a concentration sweet spot where your target dose falls at a clean, easily measurable mark on the syringe.
For context, a standard U-100 insulin syringe has 100 unit markings across 1 mL. Each small tick represents 1 unit, or 0.01 mL. Most syringes are accurate to plus or minus 0.5 units, which means your practical minimum dose resolution is about 0.005 mL. At a concentration of 2,500 mcg/mL (the standard for a 5mg vial with 2mL water), that 0.5-unit margin of error translates to roughly 12.5 mcg - perfectly acceptable for most peptide protocols.
Understanding the Math Step by Step
The reconstitution calculation is four simple arithmetic steps. Once you understand the logic, you will never need to second-guess yourself at the mixing station.
Step A: Convert Milligrams to Micrograms
Peptide vials are labeled in milligrams (mg), but doses are prescribed in micrograms (mcg). Since 1 mg equals 1,000 mcg, you multiply the vial quantity by 1,000. A 5mg vial contains 5,000 mcg of peptide. A 2mg vial contains 2,000 mcg. Simple unit conversion, but critical because skipping this step leads to 1,000x dosing errors.
Step B: Calculate Concentration
Concentration tells you how many micrograms are dissolved in each milliliter of solution. Divide the total mcg by the volume of water you added. If you put 2 mL of bacteriostatic water into a 5mg (5,000 mcg) vial, you get 2,500 mcg per mL. If you used 2.5 mL instead, the concentration drops to 2,000 mcg per mL. This is the most important number because it defines the relationship between liquid volume and drug dose for every injection from that vial.
Step C: Calculate Draw Volume
Now you can determine how much liquid to draw for your desired dose. Divide your target dose in mcg by the concentration. At 2,500 mcg/mL, a 250 mcg dose requires 0.1 mL. A 500 mcg dose requires 0.2 mL. The relationship is linear and proportional, which means doubling the dose always doubles the draw volume at the same concentration.
Step D: Convert to Insulin Syringe Units
Insulin syringes are marked in "units" rather than milliliters. On the standard U-100 syringe used for peptide injections, 100 units equals 1.0 mL. Multiply the draw volume by 100. So 0.1 mL becomes 10 units, 0.2 mL becomes 20 units, and 0.05 mL becomes 5 units. This is the number you actually look for on the syringe barrel when drawing your dose.
The 2mL Rule of Thumb
For most 5mg peptide vials, adding 2mL of bacteriostatic water creates the most convenient concentration. Common doses land on easy-to-read syringe markings: 100mcg = 4 units, 250mcg = 10 units, 500mcg = 20 units. This minimizes measurement error and makes daily dosing faster.
Common Peptide Configurations
While the calculator handles any combination, here are the most frequently used configurations in modern peptide therapy. These represent the standard-of-care dosing ranges that the majority of telehealth clinics prescribe.
| Peptide | Vial Size | Water | Typical Dose | Units to Draw |
|---|---|---|---|---|
| BPC-157 | 5 mg | 2 mL | 250 mcg | 10 units |
| TB-500 | 5 mg | 2 mL | 750 mcg | 30 units |
| Ipamorelin | 5 mg | 2.5 mL | 200 mcg | 10 units |
| CJC-1295 (no DAC) | 2 mg | 2 mL | 100 mcg | 10 units |
| Tesamorelin | 2 mg | 2 mL | 1,000 mcg | 100 units |
| GHK-Cu | 5 mg | 2 mL | 500 mcg | 20 units |
| Semax | 5 mg | 2 mL | 200 mcg | 8 units |
| Selank | 5 mg | 2 mL | 250 mcg | 10 units |
Choosing Your Water Volume
The amount of bacteriostatic water you add is not arbitrary. It should be chosen based on your prescribed dose to land at a convenient syringe marking. Here is how to think about it:
- Less water (1 mL): Creates a higher concentration. Good for large doses that would otherwise require too much liquid. Downside: smaller doses become harder to measure accurately because tiny differences in the syringe represent large mcg changes.
- Standard water (2 mL): The goldilocks zone for most 5mg vials. Doses between 100-500 mcg land between 4-20 units, which is easily readable on any insulin syringe.
- More water (3+ mL): Creates a dilute solution. Useful for very small doses (under 100 mcg) where you need finer measurement resolution. Downside: larger injection volumes can mean more discomfort and the vial runs out faster per dose.
Critical Safety Notes
- Always use bacteriostatic water (BAC water), not sterile water or saline. BAC water contains 0.9% benzyl alcohol, which prevents bacterial growth and allows multi-dose use from a single vial for up to 28 days.
- Never inject air into the peptide vial aggressively. Gently roll the vial to dissolve the lyophilized powder. Aggressive shaking can denature the peptide and reduce potency.
- Store reconstituted peptides in the refrigerator (36-46 degrees F / 2-8 degrees C). Most reconstituted peptides maintain stability for 14-28 days refrigerated.
- If the solution appears cloudy, discolored, or contains particulates after mixing, do not use it. These are signs of contamination or degradation.
Reading the Insulin Syringe
Insulin syringes come in three common sizes: 0.3 mL (30 units), 0.5 mL (50 units), and 1.0 mL (100 units). For peptide therapy, the 1.0 mL U-100 syringe is standard because most doses fall in the 5-30 unit range, and the larger barrel provides more readable tick marks in that zone.
When reading the syringe, hold it at eye level with the needle pointing up. The bottom of the plunger rubber stopper (the edge closest to the needle) is your measurement line. Always align this edge with the desired unit marking. Do not count from the top of the stopper or the middle - use the bottom edge consistently.
On a 1.0 mL syringe, each small tick represents 1 unit (0.01 mL). The numbered markings appear at every 10 units (0.1 mL). Longer tick marks without numbers typically appear at every 5 units (0.05 mL). Practically, most people can accurately measure to the nearest 1 unit, and with care, to the nearest 0.5 units.
Frequently Asked Questions
Can I use this calculator for HCG?
Yes. HCG vials are measured in International Units (IU) rather than micrograms, but the math is identical. Enter the total IU in the vial as the "Vial Quantity" (treating IU as if they were mcg), and enter your desired IU dose as the "Desired Dose." The calculator will output the correct number of syringe units. For example, a 5,000 IU vial with 2 mL of water at a 500 IU dose would be entered as 5,000 / 2 / 500, giving you 20 units.
How accurate is this calculator?
The math is precise. The only source of error is the physical act of drawing the dose on the syringe, which has a tolerance of approximately plus or minus 0.5 units on a standard U-100 syringe. The calculator rounds to the nearest 0.5 units to reflect this physical limitation. For most peptide protocols, this margin is clinically insignificant.
What if I use a 0.5 mL or 0.3 mL syringe?
The unit-to-mL conversion is the same regardless of syringe size. 10 units is always 0.1 mL. However, smaller syringes have finer tick marks in the lower range, making them more accurate for small doses (under 20 units). If your calculated dose is under 30 units, a 0.5 mL syringe will give you better precision. The visual syringe in this calculator represents a standard 1.0 mL U-100 syringe.
Can I mix two peptides in the same syringe?
Some practitioners combine compatible peptides in a single injection (for example, Ipamorelin and CJC-1295). If your provider has approved this, draw the first peptide to the required unit line, then insert the needle into the second vial and draw additional units on top. The total units drawn should equal the sum of both individual doses. However, never mix peptides in the same vial for storage - always draw and inject immediately.