Peptide Calculator
Tell it your vial. It tells you how much bacteriostatic water to add, how many units to draw for your dose, and what your schedule looks like: how long the vial lasts, when to discard it, and how many vials your cycle needs.
How many units of BPC-157 to draw
That is the draw. For the schedule, vial life, a second peptide or the cost,plan the rest below
Step 1: What are you mixing?
The amount of peptide in the vial is the starting point for every number that follows.
Freeze-dried. You add the water.
Learn more
mg or mcg?
A milligram (mg) is 1,000 micrograms (mcg). Vials are labeled in mg. Small doses are usually written in mcg.
So a 5 mg vial holds 5,000 mcg, and a 250 mcg dose is a quarter of one milligram.
If a number looks a thousand times too big or too small, the unit is probably wrong. The calculator spots that pattern and offers a one-tap fix.
Pre-mixed and compounded vials
Some vials arrive as liquid: compounded semaglutide or tirzepatide from a pharmacy, or a supplier who mixes for you. There is nothing to add.
Choose "Already liquid" and enter the strength printed on the label, usually in mg/mL. If the label gives total mg in total mL (for example 10 mg in 2 mL), divide the two: that is 5 mg/mL.
The calculator then skips the water step and goes straight to units. Storage instructions from the pharmacy override the discard date shown here.
Step 2: How much water?
Water sets the concentration, and concentration decides how far you pull the plunger.
Add 2 mL, the amount most people use for this vial. That makes 2.5 mg/mL, so a 250 mcg dose is 10 units on a 0.5 mL syringe, easy to read.
Compare volumes and choose the water
Preserved. Keeps about 4 weeks in the fridge.
Learn more
More water does not change your dose
The peptide in the vial is fixed. Water only spreads it out.
Add 1 mL to a 5 mg vial and each unit on the syringe holds 50 mcg. Add 2 mL and each unit holds 25 mcg. For the same 250 mcg you draw 5 units or 10 units. Same dose, different plunger position.
Use that to your advantage. More water makes tiny doses easier to read. Less water keeps big doses inside the barrel.
How much liquid a vial can take
Most peptide vials are small glass vials with about 3 mL of room. Some hold 2 mL.
The powder takes up almost no space, so a 3 mL vial can take around 2.5 to 3 mL of water before it is full to the stopper.
If the calculator suggests more water than your vial can hold, switch to a narrower syringe instead (the 0.3 mL barrel has the widest tick spacing), or buy a smaller vial. Never overfill: the pressure pushes liquid back out around the needle.
Why bacteriostatic water
Bacteriostatic water is sterile water with 0.9% benzyl alcohol added.
The benzyl alcohol stops bacteria growing inside the vial between doses. That is what lets you draw from the same vial for about 4 weeks.
Plain sterile water dissolves the powder just as well, but it has no preservative, so a vial mixed with it should be used within a day.
How to mix the vial
- Wash your hands. Lay out the vial, the bacteriostatic water, a mixing syringe (a plain 1 mL or 3 mL syringe is fine), alcohol swabs and your insulin syringes.
- Pop the caps and wipe both rubber stoppers with a fresh alcohol swab. Let them air-dry for about 10 seconds.
- Draw the water. Pull the volume from Step 2 into the mixing syringe and tap out any air bubbles.
- Push the water in slowly. Aim the needle at the glass wall so the water runs down the side instead of hitting the powder. Hitting the powder makes foam.
- Dissolve by rolling the vial gently between your palms until the liquid is clear. Do not shake. If a few specks remain, give it a minute in the fridge and roll again.
- Write the date on the vial and stand it upright in the fridge. Your discard date is on the dose card.
Step 3: What is your dose?
The dose turns concentration into a number of units you can read straight off the syringe.
Usual range: 250 mcg to 500 mcg
250 mcg once daily
- Usual range
- 250 mcg to 500 mcg
- Typical course
- 8 weeks
Often dosed 1-2x daily
The most common peptide syringe. Easy to read up to 50 units.
Dose by body weight and syringe help
A set amount per injection, in mcg or mg.
Learn more
Reading units on a U-100 syringe
A U-100 insulin syringe is marked in units. 100 units is 1 mL, so 1 unit is 0.01 mL.
The calculator converts your dose straight into units, so you read the answer off the barrel with no math.
Pull the plunger until the top of the black rubber stopper lines up with the tick. On a 1 mL barrel the small ticks are 2 units apart. On a 0.5 mL barrel they are 1 unit apart. On a 0.3 mL barrel they are 1 unit, sometimes half a unit.
Which syringe to use
All three barrels are U-100 insulin syringes. Only the size changes.
1 mL (100 units) fits the biggest draws. 0.5 mL (50 units) is the most common for peptides and easy to read. 0.3 mL (30 units) has the widest tick spacing, best when your draw is under about 10 units.
A 29 to 31 gauge needle, 5/16 to 1/2 inch long, suits injections under the skin. The calculator warns you if a draw will not fit, or is too small to read, on the barrel you picked.
Check the syringe says U-100, not U-40
U-40 syringes exist for pet insulin. They have 40 units per mL, not 100.
Every number in this calculator assumes U-100. Draw a U-100 unit count on a U-40 syringe and you inject two and a half times the liquid.
Look for "U-100" printed on the barrel or the box. If it says U-40, do not use these numbers.
Dosing by body weight
Some peptides are dosed per kilogram. Multiply your weight in kg by the mcg/kg figure to get the dose per injection.
80 kg at 5 mcg/kg is 400 mcg. If you weigh in pounds, divide by 2.2 first: 176 lb is 80 kg.
Enter your weight and the mcg/kg and the calculator does this for you, then converts the result into units.
More tools
How to Reconstitute Peptides
Reconstitution means dissolving the freeze-dried powder in bacteriostatic water. Pick your peptide and vial in the calculator above, use the water amount it suggests, and enter your dose to get the units to draw. Then follow these steps every time you open a new vial.
- 1
Set up a clean space
Wash your hands. Lay out the peptide vial, bacteriostatic water, alcohol swabs, a mixing syringe and your insulin syringes on a clean, flat surface.
- 2
Wipe both stoppers
Remove the caps and wipe the rubber stoppers of the peptide vial and the water bottle with a fresh 70% alcohol swab. Let them air-dry for about 10 seconds.
- 3
Draw the water
Pull the volume the calculator gives you (for example 2 mL for a 5 mg vial) into the mixing syringe. Tap out any air bubbles.
- 4
Add the water slowly
Push the needle through the peptide vial stopper and aim at the glass wall so the water runs down the side. Do not spray it onto the powder; that causes foaming.
- 5
Roll, do not shake
Roll the vial gently between your palms until the liquid is completely clear. Shaking can damage the peptide.
- 6
Label and refrigerate
Write the date on the vial and stand it upright in the fridge at 2 to 8 °C. Draw each dose with a fresh insulin syringe and discard the vial on the date the calculator shows.
How Much Bacteriostatic Water to Add
The water decides the concentration, and the concentration decides how much liquid one dose is. More water makes small doses easier to read on the syringe; less water keeps the injection small. These are the starting points the calculator loads for common peptides.
BPC-157
- Vial
- 5 mg
- BAC water
- 2 mL
- Concentration
- 2.5 mg/mL
- Usual dose
- 250 mcg to 500 mcg, 1×/day
TB-500
- Vial
- 10 mg
- BAC water
- 2 mL
- Concentration
- 5 mg/mL
- Usual dose
- 2 mg to 2.5 mg, 2×/week
Semaglutide
- Vial
- 5 mg
- BAC water
- 2 mL
- Concentration
- 2.5 mg/mL
- Usual dose
- 250 mcg to 2.4 mg, Weekly
Tirzepatide
- Vial
- 5 mg
- BAC water
- 2 mL
- Concentration
- 2.5 mg/mL
- Usual dose
- 2.5 mg to 15 mg, Weekly
Retatrutide
- Vial
- 10 mg
- BAC water
- 2 mL
- Concentration
- 5 mg/mL
- Usual dose
- 1 mg to 12 mg, Weekly
CJC-1295 (No DAC)
- Vial
- 2 mg
- BAC water
- 2 mL
- Concentration
- 1 mg/mL
- Usual dose
- 100 mcg to 300 mcg, 1×/day
Ipamorelin
- Vial
- 5 mg
- BAC water
- 2 mL
- Concentration
- 2.5 mg/mL
- Usual dose
- 100 mcg to 300 mcg, 2×/day
GHK-Cu
- Vial
- 50 mg
- BAC water
- 5 mL
- Concentration
- 10 mg/mL
- Usual dose
- 1 mg to 2 mg, 1×/day
Tesamorelin
- Vial
- 5 mg
- BAC water
- 2.5 mL
- Concentration
- 2 mg/mL
- Usual dose
- 1 mg to 2 mg, 1×/day
PT-141
- Vial
- 10 mg
- BAC water
- 2 mL
- Concentration
- 5 mg/mL
- Usual dose
- 500 mcg to 1.75 mg, As needed
MOTS-c
- Vial
- 10 mg
- BAC water
- 1 mL
- Concentration
- 10 mg/mL
- Usual dose
- 2.5 mg to 10 mg, 3×/week
SS-31
- Vial
- 50 mg
- BAC water
- 1 mL
- Concentration
- 50 mg/mL
- Usual dose
- 10 mg to 40 mg, 1×/day
Starting points, not rules. Put your own vial size and dose into the calculator above for exact numbers.
Syringe Unit Conversion Chart
On a U-100 insulin syringe, 100 units is 1 mL, so one unit is 0.01 mL. Units to draw = dose in mg ÷ concentration in mg/mL × 100.
| Dose | at 2.5 mg/mL | at 5 mg/mL | at 10 mg/mL |
|---|---|---|---|
| 100 mcg | 4 units | 2 units | 1 units |
| 250 mcg | 10 units | 5 units | 2.5 units |
| 500 mcg | 20 units | 10 units | 5 units |
| 1 mg | 40 units | 20 units | 10 units |
| 2 mg | 80 units | 40 units | 20 units |
| 2.5 mg | 100 units | 50 units | 25 units |
| 5 mg | over 100 units | 100 units | 50 units |
Over 100 units does not fit a 1 mL insulin syringe. Add more water to dilute, or split the dose.
Peptide Calculator FAQ
How much bacteriostatic water do I add to a peptide vial?
Enough to make your dose land on an easy-to-read tick. A common starting point is 1 mL per 5 mg of powder, so a 5 mg vial gets 1 mL and a 10 mg vial gets 2 mL. For small doses like 250 mcg of BPC-157, 2 mL in a 5 mg vial gives a 10-unit draw, which is easier to read than 5 units. The Water step shows every option side by side.
What does a peptide reconstitution calculator do?
It turns three numbers, the mg in your vial, the mL of water you add and the dose you want, into one answer: how many units to pull on your syringe. It also gives the concentration, how many doses the vial holds and when to throw it out. The point is to take the arithmetic out of the moment you are holding a needle.
What syringe do I use for peptide injections?
A U-100 insulin syringe, which means 100 units per mL, with a fixed 29 to 31 gauge needle. They come in 0.3 mL, 0.5 mL and 1 mL sizes and are sold at most pharmacies. Do not use a U-40 syringe; its units are a different size.
How do I convert mcg to units on an insulin syringe?
Work out the strength first: vial mg divided by water mL gives mg/mL. Multiply by 10 and you have mcg per unit, then divide your dose by that. Example: 5 mg in 2 mL is 2.5 mg/mL, so 25 mcg per unit, so a 250 mcg dose is 10 units.
How long does a reconstituted peptide last?
Mixed with bacteriostatic water and kept in the fridge at 2 to 8 °C (36 to 46 °F), most peptides are good for about 4 weeks. The calculator assumes 30 days unless the peptide has its own figure. Mixed with plain sterile water, use it the same day. Never freeze a mixed vial.
Can I use this calculator for semaglutide, tirzepatide or retatrutide?
Yes. For a powder vial, use it like any other peptide. For a compounded vial that arrives as liquid, choose the pre-mixed option and enter the mg/mL on the label. The Schedule step also has weekly titration ladders for the GLP-1 peptides, so the draw steps up with you.
How much water do I add to a pre-mixed or compounded vial?
None. A pre-mixed vial is already at its final strength. Choose the pre-mixed option and enter the concentration from the label in mg/mL. If the label gives total mg and total mL instead, divide the two: 10 mg in 2 mL is 5 mg/mL.
Does adding more water change my dose?
No. The peptide in the vial is fixed; water only changes how much liquid carries each dose. More water means more units for the same mcg, which makes tiny doses easier to read, and less water keeps big doses from overflowing the syringe. Your dose in mcg is the same either way.
This calculator does the arithmetic. It is not medical advice. Confirm every dose with a qualified professional before you inject anything, and use a fresh sterile needle every time.