Peptide Calculators
Last updated: June 2026
Reconstitution mg-to-mL Concentration Chart for Any Vial
After you add bacteriostatic water to a lyophilised vial, the final concentration is just the vial strength divided by the water volume. This chart maps any vial strength and water volume to a final mg/mL so you can read the number off a table instead of guessing.
The reconstitution concentration chart mg per mL: how the number is made
Reconstitution does not create or destroy the drug. A vial holds a fixed mass of powder, measured in milligrams (mg). When you add bacteriostatic water, that fixed mass spreads through the liquid you added. The final concentration is the mass divided by the liquid volume:
Concentration (mg/mL) = vial strength (mg) ÷ water added (mL)
This is the single equation behind every row of the reconstitution concentration chart below. The powder volume itself is tiny and is treated as negligible for typical research-peptide and small-protein vials, so the final volume is taken as the water you injected into the vial. For an explanation of the underlying ratio, see how mg/mL works and concentration explained simply.
Example
A 10 mg vial reconstituted with 2 mL of bacteriostatic water gives 10 ÷ 2 = 5 mg/mL. The same 10 mg vial with 1 mL gives 10 ÷ 1 = 10 mg/mL. More water, same drug, lower concentration.
Full mg-to-mL concentration chart
Each cell is vial strength ÷ water volume, rounded to a sensible number of digits. Read down to your vial strength, across to the water volume you plan to add, and the cell is the final mg/mL.
| Vial strength | 1 mL water | 2 mL water | 3 mL water | 5 mL water |
|---|---|---|---|---|
| 5 mg | 5 mg/mL | 2.5 mg/mL | 1.67 mg/mL | 1 mg/mL |
| 10 mg | 10 mg/mL | 5 mg/mL | 3.33 mg/mL | 2 mg/mL |
| 15 mg | 15 mg/mL | 7.5 mg/mL | 5 mg/mL | 3 mg/mL |
| 20 mg | 20 mg/mL | 10 mg/mL | 6.67 mg/mL | 4 mg/mL |
| 30 mg | 30 mg/mL | 15 mg/mL | 10 mg/mL | 6 mg/mL |
| 50 mg | 50 mg/mL | 25 mg/mL | 16.67 mg/mL | 10 mg/mL |
If your vial or water volume is not in the table, use the equation directly, or let the reconstitution calculator compute it for any combination, including odd numbers like 12.5 mg or 1.5 mL.
Converting concentration into syringe units and dose volume
The concentration tells you how much drug is in each mL, but you dose by drawing a volume into a syringe. Two more steps connect concentration to what you draw:
Dose volume (mL) = dose (mg) ÷ concentration (mg/mL)
Syringe units (on a U-100 insulin syringe) = dose volume (mL) × 100
A U-100 insulin syringe is marked so that 100 units equals 1 mL, so each unit is 0.01 mL regardless of what drug is inside. See mg, mcg, mL and units explained for the full unit chain.
Example
A 10 mg vial with 2 mL water is 5 mg/mL. To take a 0.5 mg dose: 0.5 ÷ 5 = 0.1 mL. On a U-100 syringe that is 0.1 × 100 = 10 units. If you instead reconstituted the same vial with 1 mL (10 mg/mL), the same 0.5 mg dose would be 0.05 mL, or 5 units — half the volume because the concentration doubled.
Worked example for a peptide vial in micrograms
Many peptides are dosed in micrograms (mcg). The chart still works — you just keep your units consistent. 1 mg = 1000 mcg, so a 5 mg vial holds 5000 mcg.
Example
A 5 mg vial reconstituted with 2 mL of bacteriostatic water is 2.5 mg/mL, which is the same as 2500 mcg/mL. For a 250 mcg dose: 250 ÷ 2500 = 0.1 mL = 10 units. Doubling the water to 4 mL would give 1250 mcg/mL, and the same 250 mcg dose would then be 0.2 mL, or 20 units.
Choosing the water volume so a common dose lands on a round, easy-to-read unit mark reduces measuring error. How much bac water should I add walks through picking a volume on purpose rather than by habit.
Why the same vial can give very different syringe readings
Two people with identical 10 mg vials can draw very different unit counts for the same milligram dose, purely because they added different amounts of water. The drug per dose is identical; only the volume changes.
| Water added to 10 mg vial | Concentration | Volume for a 1 mg dose | Units (U-100) |
|---|---|---|---|
| 1 mL | 10 mg/mL | 0.10 mL | 10 units |
| 2 mL | 5 mg/mL | 0.20 mL | 20 units |
| 4 mL | 2.5 mg/mL | 0.40 mL | 40 units |
This is why a unit count copied from someone else is meaningless unless their vial strength and water volume match yours exactly. Always re-derive from your own numbers, or check them in the reconstitution calculator. The related idea of working backward from a target unit count is covered in the reverse peptide calculator guide.
What this chart does not tell you
The chart is arithmetic only. It tells you the concentration and the volume to draw; it says nothing about whether a given dose is appropriate, safe, or supported by evidence for any specific compound. Several substances often discussed alongside reconstitution — including research peptides such as BPC-157 and TB-500, and newer agents like retatrutide — are unapproved drugs with little to no reliable human safety or dosing data, and regulators warn they are not safe to self-administer without medical supervision. Use this tool to check measurement math, not to decide what or how much to take.
Bacteriostatic water contains 0.9 percent benzyl alcohol as a preservative and is intended for multi-dose reconstitution; it is not interchangeable with sterile water for every product, and benzyl alcohol carries specific cautions in neonates. Follow the directions on the specific product label. For background on the diluent itself, see what is bac water and what does reconstitution mean.
FAQs
How do I calculate mg/mL after reconstitution?
Divide the vial strength in milligrams by the volume of water you added in millilitres. A 10 mg vial plus 2 mL of bacteriostatic water is 10 / 2 = 5 mg/mL. The powder volume is negligible, so the final volume is taken as the water you added.
Does adding more water change the dose?
No. The mass of drug in the vial is fixed. Adding more water lowers the concentration, so you draw a larger volume for the same milligram dose. The drug delivered per dose is unchanged; only the syringe volume and unit reading change.
How do I turn a concentration into syringe units?
First find the dose volume: dose (mg) divided by concentration (mg/mL). Then multiply that volume in mL by 100 to get units on a U-100 insulin syringe, where 100 units equals 1 mL. For example, 0.1 mL is 10 units.
Can I use this chart for peptides measured in micrograms?
Yes. Convert using 1 mg = 1000 mcg and keep your units consistent. A 5 mg vial in 2 mL is 2.5 mg/mL, which equals 2500 mcg/mL, so a 250 mcg dose is 0.1 mL or 10 units.
Is there one correct water volume for a vial?
No single volume is required. Any volume gives a valid concentration as long as you do the math. People often pick a volume that makes a common dose land on a round, easy-to-read unit mark, which reduces measuring error.
Read next
Peptide Reconstitution Calculator GuideSources
- BACTERIOSTATIC WATER injection, solution — full prescribing label. DailyMed, U.S. National Library of Medicine. dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=87d6e9dc-fe3b-4593-ac9a-d7493d1959c7.
- BACTERIOSTATIC WATER injection, solution — WARNING: Not for use in neonates. DailyMed, U.S. National Library of Medicine. dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=87d6e9dc-fe3b-4593-ac9a-d7493d1959c7.
- Giving an Insulin Injection — patient care sheet. UF Health, University of Florida Health. ufhealth.org/care-sheets/giving-an-insulin-injection.
- BPC-157: a prohibited peptide and an unapproved drug found in health and wellness products. Operation Supplement Safety (OPSS), U.S. Department of Defense / Uniformed Services University. www.opss.org/article/bpc-157-prohibited-peptide-and-unapproved-drug-found-health-and-wellness-products.
- ISMP Guidelines for Sterile Compounding and the Safe Use of Sterile Compounding Technology. Institute for Safe Medication Practices. www.ismp.org/system/files/resources/2022-04/ISMP195-Compouding%20Guidelines%20v1-042722-2.pdf.
This guide is for general educational purposes only and does not constitute medical advice. Always follow your prescriber's specific instructions.