What does this calculator do?

It converts your peptide dose into the exact number of syringe units to draw. You provide three inputs: vial size (mg), water added (ml), and your target dose (mcg). The calculator handles the concentration math and tells you where to pull the plunger.

How does reconstitution work?

Peptides ship as freeze-dried powder. You add bacteriostatic water to dissolve the powder into an injectable solution. The amount of water you choose determines the concentration, which in turn determines how many syringe units equal your dose. More water means a more dilute solution (more units per dose). Less water means more concentrated (fewer units per dose).

What is the formula behind the result?

Three steps. First, divide the vial size by the water volume to get the concentration in mg/ml. Second, convert your dose to mg and divide by the concentration to get the injection volume in ml. Third, multiply by 100 to convert ml to syringe units. Example: 5 mg vial, 2 ml water, 250 mcg dose = 2.5 mg/ml concentration, 0.1 ml volume, 10 units.

How much water should I add?

There is no single right answer. The water volume is a trade-off between precision and convenience. Less water (1 ml) gives you fewer units per dose, which can be harder to measure precisely on a small syringe. More water (2-3 ml) spreads the dose across more units, making it easier to draw accurately. Most people use 1-2 ml for standard vials.

What is the difference between mg and mcg?

1 mg equals 1,000 mcg. Vials are labeled in milligrams (mg) because they contain larger quantities. Individual doses are typically measured in micrograms (mcg) because you inject a small fraction of the vial each time. A 5 mg vial contains 5,000 mcg total.

What do the numbers on an insulin syringe mean?

They measure volume in units. One unit equals 0.01 ml on any insulin syringe, regardless of size. A 30-unit syringe holds 0.3 ml total. A 100-unit syringe holds 1.0 ml total. The markings exist to make small volumes easier to measure than working in fractions of a milliliter.

How do I know how many doses are in a vial?

Divide the total content (in mcg) by your dose per injection (in mcg). A 5 mg vial holds 5,000 mcg. At 250 mcg per dose, that is 20 injections. The water volume does not affect the number of doses. It only changes how many units you draw each time.

Does the syringe size affect the dose?

No. All insulin syringes deliver 100 units per ml. A 30-unit, 50-unit, and 100-unit syringe use the same scale. The only difference is how much liquid the syringe can hold. If your dose requires 15 units, any of the three sizes will work. If it requires 60 units, you need a 100-unit syringe.

Why use bacteriostatic water instead of sterile water?

Bacteriostatic water contains 0.9% benzyl alcohol as a preservative. This allows you to draw from the same vial multiple times over 3-4 weeks without contamination. Sterile water has no preservative, so reconstituted peptides must be used within 24 hours. For any multi-dose vial, BAC water is the standard.

How long does a reconstituted peptide stay good?

Refrigerated at 2-8 degrees C with bacteriostatic water: 3-4 weeks. Frozen at -20 degrees C in single-use aliquots: 3-4 months. Unreconstituted powder is far more stable and can sit at room temperature for weeks or frozen for years. Only mix what you plan to use within a few weeks.

Which syringe size should I use?

Match the syringe to your typical dose volume. If your dose is under 30 units, a 0.3 ml (30-unit) syringe gives you the finest markings and easiest precision. For doses between 30-50 units, use a 0.5 ml syringe. For anything larger, use 1.0 ml. Most subcutaneous peptide doses fall in the 5-20 unit range, making the 30-unit syringe ideal.

Is this calculator free?

Yes. No account, no paywall, no limitations. Use it whenever you need it.

Peptide Calculator

Three inputs. One answer. Enter your vial size, water volume, and target dose, and get the exact syringe units to draw. No mental math, no guessing.

What is the total volume of your syringe?

How many milligrams are in your peptide vial?

How much bacteriostatic water are you adding?

How much peptide do you want per dose?

Select your vial size, water amount, and dose above to see your result.

Reconstitution in four steps

Peptides arrive as freeze-dried powder. You mix them with bacteriostatic water to create an injectable solution. Proper technique keeps the peptide intact and your doses accurate.

Clean setup

Sterile gloves, clean surface. Have your peptide vial, BAC water, insulin syringe, and alcohol swabs ready before you start.

Warm to room temperature

If either vial was refrigerated or frozen, let it sit at room temperature (20-25 degrees C) first. Cold liquid causes foaming and poor dissolution.

Add water slowly

Swab both vial tops with alcohol. Draw your BAC water and inject it against the inner glass wall at a 45-degree angle. Do not spray it onto the powder directly.

Swirl, never shake

Gently roll or swirl the vial until the solution is completely clear. Aggressive shaking damages peptide bonds. If it stays cloudy, give it more time.

Unsure how much water to use?
Water volume controls concentration. Less water = fewer units per dose (harder to measure small amounts). More water = more units per dose (easier precision). Try different amounts in the calculator above to see how it changes your syringe draw.

Storage after mixing

Once reconstituted, temperature is everything. The peptide is now in solution and degrades faster than powder. Two options depending on your timeline.

Refrigerated (3-4 weeks)

Keep at 2-8 degrees C in the main compartment of your fridge. Avoid the door shelf where temperature swings on every open. Store upright, stopper facing up.

Frozen (3-4 months)

Split into single-use aliquots and freeze at -20 degrees C. Each freeze-thaw cycle degrades the peptide, so only thaw what you intend to use. Do not refreeze.

Powder is more forgiving. Unreconstituted peptide can sit at room temperature for weeks or stay frozen for years. Only mix what you will actually use in the next few weeks.

The math behind every result

The calculator above does this automatically, but here is the three-step formula so you can verify any result by hand. Worked example: 5 mg vial, 2 ml BAC water, 250 mcg dose.

Concentration

Vial size divided by water volume. This tells you how much peptide is in each ml of solution.

5 mg ÷ 2 ml = 2.5 mg/ml

Injection volume

Your dose (converted to mg) divided by the concentration. This is the actual liquid volume you inject.

250 mcg ÷ (2.5 × 1,000) = 0.1 ml

Syringe units

Injection volume times 100. Every insulin syringe marks 100 units per ml, so this gives you the exact tick mark.

0.1 ml × 100 = 10 units

Common setups by peptide

Typical reconstitution configurations for popular peptides. Expand any entry to see the math, then load those values into the calculator.

5 mg vial · 2 ml BAC water · 250 mcg dose · 1-2x daily

One of the most widely used repair peptides. A 5 mg vial with 2 ml water gives you a 2.5 mg/ml solution. At 250 mcg per injection, that is 10 units on the syringe and 20 total doses from a single vial.

Quick-reference chart

Pre-calculated syringe units for the most common vial and water combinations. All values assume a 100-unit (1 ml) insulin syringe. A dash means the dose exceeds syringe capacity at that concentration.

How to use: Find your vial size and water volume on the left, then read across to your dose column. The number is the unit mark on your syringe.

Example: 5 mg vial + 2 ml water + 250 mcg dose = 10 units.

Vial	BAC Water	Conc.	250 mcg	500 mcg	1 mg	2.5 mg	5 mg
2 mg	1 ml	2 mg/ml	12.5	25	50	—	—
2 mg	2 ml	1 mg/ml	25	50	100	—	—
5 mg	1 ml	5 mg/ml	5	10	20	50	100
5 mg	2 ml	2.5 mg/ml	10	20	40	100	—
5 mg	3 ml	1.67 mg/ml	15	30	60	—	—
10 mg	1 ml	10 mg/ml	2.5	5	10	25	50
10 mg	2 ml	5 mg/ml	5	10	20	50	100
10 mg	3 ml	3.33 mg/ml	7.5	15	30	75	—
15 mg	2 ml	7.5 mg/ml	3.3	6.7	13.3	33.3	66.7
15 mg	3 ml	5 mg/ml	5	10	20	50	100

Units and conversions

Peptide dosing involves five different units. Most confusion comes from mixing up weight (mg, mcg) with volume (ml, units). Here is what each one measures and when you encounter it.

Unit	Full Name	Measures	Used For
mg	Milligram	Weight	How much peptide is in a vial
mcg	Microgram	Weight	How much peptide per injection
ml	Milliliter	Volume	BAC water volume and injection volume
IU	International Unit	Biological activity	Dosing for HGH and certain hormones
Units	Syringe Units	Volume (markings)	The markings on insulin syringes

Key Conversion

1 mg = 1,000 mcg

A 5 mg vial contains 5,000 mcg total

Syringe Unit to Volume

1 unit = 0.01 ml

30-unit = 0.3 ml, 50-unit = 0.5 ml, 100-unit = 1.0 ml

Peptide dosing at a glance

Typical vial sizes, water volumes, and dose ranges for popular peptides. These are general starting points. Your protocol may differ based on your health profile and goals.

Peptide	Category	Vial Size	Typical Water	Common Dose
BPC-157	Tissue Repair	5 mg	1-2 ml	250-500 mcg
Semaglutide	Weight Loss	5 mg, 10 mg	2-2.5 ml	0.25-2.4 mg
Tirzepatide	Weight Loss	5 mg, 10 mg, 15 mg	2-3 ml	2.5-15 mg
TB-500	Tissue Repair	5 mg, 10 mg	1-2 ml	2-5 mg
CJC-1295 / Ipamorelin	Growth Hormone	5 mg blend	2.5 ml	300 mcg
Sermorelin	Growth Hormone	5 mg, 9 mg, 15 mg	2-3 ml	200-500 mcg
AOD-9604	Weight Loss	5 mg	2 ml	300 mcg
PT-141	Sexual Wellness	10 mg	2 ml	1-2 mg

Common questions

Everything else about reconstitution, dosing math, and syringe selection.

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