How do you calculate peptide concentration after reconstitution?

Divide the mass of peptide in the vial by the volume of bacteriostatic water added. A 10 mg vial reconstituted with 2 mL of diluent gives 5 mg/mL, which is 5000 mcg per mL.

How do you convert a dose in milligrams to syringe units?

First divide the dose by the concentration to get a volume in millilitres, then multiply by the syringe's units per millilitre. On a U-100 syringe there are 100 units per millilitre, so 0.5 mL is 50 units.

How much bacteriostatic water should be added to a vial?

Whatever volume produces a concentration that makes the measurement you need easy to read on your syringe. Volume equals vial mass divided by target concentration: a 10 mg vial at a 5 mg/mL target needs 2 mL.

What is the difference between units and milligrams?

Units are a volume marking on an insulin syringe, not an amount of drug. One unit on a U-100 syringe is always 0.01 mL. How much peptide sits in that 0.01 mL depends entirely on the concentration you mixed.

Is bacteriostatic water the same as sterile water?

No. Bacteriostatic water contains roughly 0.9% benzyl alcohol as a preservative, which inhibits bacterial growth and is why multi-use vials are usually reconstituted with it. Sterile water contains no preservative.

Does this calculator tell me what dose to take?

No. It performs arithmetic on numbers you enter. GLPWiki publishes no dosing protocols. Dosing decisions belong with a licensed clinician.

TOOLS

Peptide calculators

Three linked tools for the arithmetic behind reconstitution: concentration after mixing, how much bacteriostatic water to add, and how many syringe units a given volume corresponds to. Everything updates live and every result is shareable — the numbers live in the page URL.

IMPORTANT — READ FIRST

This tool is an educational and research reference only. It performs arithmetic on numbers you type in. It does not know what you are measuring and does not recommend anything.
It is not medical advice and is not intended to diagnose, treat, cure or prevent any disease.
Consult a licensed clinician or qualified pharmacist before acting on any calculation. Prescription medicines should be prepared and administered exactly as directed on their approved labelling.
Peptides, bacteriostatic diluents, syringes and reconstitution carry legal, sterility and safety constraints that vary by jurisdiction. Many compounds discussed on GLPWiki are investigational research chemicals with no approved human indication and no legitimate consumer supply route.
GLPWiki does not sell, source, endorse or link to suppliers, and publishes no dosing protocols.

SYRINGE

U-100: 100 units = 1 mL

The arithmetic, written out

Nothing here is hidden in JavaScript. These are the four equations the tools above evaluate, and you can check any result by hand.

CONCENTRATION: concentration (mg/mL) = vial mg ÷ bacteriostatic water mL
VOLUME TO DRAW: draw mL = dose mg ÷ concentration (mg/mL)
SYRINGE UNITS (U-100): units = draw mL × 100
MASS CONVERSION: 1 mg = 1000 mcg · 1 mcg = 0.001 mg

For other syringe barrels, swap the multiplier: a U-50 barrel is 50 units per mL and a U-40 barrel is 40 units per mL, so the same 0.2 mL reads as 20, 10 and 8 units respectively.

Syringe units are not IU. A syringe unit is a volume marking — on a U-100 barrel one unit is 0.01 mL, whatever is dissolved in it. An International Unit (IU) is a biological activity measure defined separately for each substance, and no fixed number of IU corresponds to a millilitre or a milligram. Never treat a number written on a barrel as an IU value.

CALCULATOR A

Syringe draw calculator

The scenario most people arrive with: water is already in the vial and the question is simply how far up the barrel to pull.

I added bacteriostatic water in mL mL of bacteriostatic water to a vial amount mg vial. I need required amount mg. How much do I draw?

DRAW TO

—

U-100 UNITS

—

AT 0 MG/ML

U-100 SYRINGE · SHADED TO 0 UNITS OF 100

QUICK REFERENCE · U-100 UNITS TO MILLILITRES

UNITS	10	20	30	40	50	60	70	80	90	100
ML	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1

CALCULATOR B

Peptide reconstitution calculator

Enter what is in the vial, how much bacteriostatic water you are adding and the amount you want to measure. The tool returns the resulting concentration, the volume that amount occupies, and the equivalent syringe units.

PEPTIDE IN VIAL

BACTERIOSTATIC WATER ADDED

DESIRED AMOUNT

VOLUME TO DRAW

0.000 mL

U-100 UNITS

0.0

CONCENTRATION

0.000 mg/mL

CONCENTRATION

0 mcg/mL

DOSES PER VIAL

VOLUME LEFT AFTER ONE DRAW

0.000 mL

All results start at zero. Type a vial amount, a diluent volume and a desired amount on the left and every figure here updates as you type.

CALCULATOR C

Bacteriostatic water calculator

Work the problem backwards: pick the concentration you want to end up with and the tool returns the diluent volume that produces it, plus a table of common fractions of the vial.

PEPTIDE IN VIAL

TARGET CONCENTRATION

mg/mL

A higher target concentration means less water and a smaller, harder-to-read draw. A lower one means more water and a larger, easier-to-read draw, limited by the capacity of the vial and the syringe.

BACTERIOSTATIC WATER TO ADD

2 mL

RESULTING CONCENTRATION

5 mg/mL

SAMPLE AMOUNTS AT THIS CONCENTRATION

AMOUNT (MG)	AMOUNT (MCG)	VOLUME (ML)	U-100 UNITS
0.5	500	0.1	10
1	1,000	0.2	20
1.25	1,250	0.25	25
2	2,000	0.4	40
2.5	2,500	0.5	50
5	5,000	1	100
10	10,000	2	200

Learn the reasoning behind the numbers

GUIDE

Reconstitution and bacteriostatic water

What the diluent is, where the arithmetic comes from and the mistakes that cause it to go wrong.

GUIDE

How to read a U-100 syringe

Units are a volume marking, not an amount of drug. This is the distinction most errors turn on.

GUIDE

Storage, stability and handling

Cold chain, freeze-thaw, light and the practical limits on how long a reconstituted vial stays intact.

Calculator questions

How do you calculate peptide concentration after reconstitution?: Divide the mass of peptide in the vial by the volume of bacteriostatic water added. A 10 mg vial reconstituted with 2 mL of diluent gives 5 mg/mL, which is 5000 mcg per mL.
How do you convert a dose in milligrams to syringe units?: First divide the dose by the concentration to get a volume in millilitres, then multiply by the syringe's units per millilitre. On a U-100 syringe there are 100 units per millilitre, so 0.5 mL is 50 units.
How much bacteriostatic water should be added to a vial?: Whatever volume produces a concentration that makes the measurement you need easy to read on your syringe. Volume equals vial mass divided by target concentration: a 10 mg vial at a 5 mg/mL target needs 2 mL.
What is the difference between units and milligrams?: Units are a volume marking on an insulin syringe, not an amount of drug. One unit on a U-100 syringe is always 0.01 mL. How much peptide sits in that 0.01 mL depends entirely on the concentration you mixed.
Is bacteriostatic water the same as sterile water?: No. Bacteriostatic water contains roughly 0.9% benzyl alcohol as a preservative, which inhibits bacterial growth and is why multi-use vials are usually reconstituted with it. Sterile water contains no preservative.
Does this calculator tell me what dose to take?: No. It performs arithmetic on numbers you enter. GLPWiki publishes no dosing protocols. Dosing decisions belong with a licensed clinician.

EDUCATIONAL REFERENCE ONLY · Not medical advice. Nothing here diagnoses, treats, cures or prevents any disease, and nothing here is a dosing recommendation. Consult a licensed clinician before any treatment decision.