Reconstitution Calculator

Peptide Calculator: Dosage, Reconstitution & BAC Water

Peptide calculator for reconstitution: 2 mL of BAC water is 200 units on a standard U-100 insulin syringe, and 3 mL is 300 units, because 1 unit is 0.01 mL.⁸ For BPC-157 specifically, the BPC-157 dosing chart gives these units for 5, 10 and 20 mg vials.

Enter the vial size, the BAC water you add and your dose to get the concentration, the syringe units per dose and the doses per vial. It works for any freeze-dried (lyophilized) research peptide. Before you pick a figure to enter, the peptide dosage chart shows which peptides have a published human dose and which have none. The tanning peptides make the gap plain: our Melanotan 1 vs 2 comparison puts one approved implant schedule beside a record built mostly from case reports.

Quick presets

Click a peptide to load a typical vial size. The dose that loads with it is an arbitrary example value used only to demonstrate the arithmetic, not a typical or starting dose. Enter your own dose below.

Vial & dose inputs

Total peptide in vial5 mg

1 mg100 mg

BAC water added2 mL

0.5 mL5 mL

Desired dose per injection (mcg)0 mcg

0 mcg20000 mcg

Or type the dosemcg

Dose unit

Insulin syringe size

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BAC water in mL to insulin units

On a U-100 insulin syringe, 1 mL of liquid is 100 units, so millilitres of bacteriostatic water convert straight across to syringe units. This is arithmetic for reading a syringe, not a dose.⁸ To keep this conversion beside the bac water volumes and storage limits on paper, print the peptide cheat sheet.

BAC water	Units on a U-100 syringe
0.5 mL	50 units
1 mL	100 units (one full 1 mL syringe)
2 mL	200 units (two full syringes)
3 mL	300 units (three full syringes)

A U-100 insulin syringe holds at most 100 units, which is 1 mL, so 2 mL and 3 mL are more than one syringe can draw at once (1 unit = 0.01 mL).⁸

Many KLOW pages quote their unit counts for a 3 mL fill; our KLOW peptide dosage chart converts those counts to 1, 4 and 5 mL so the amount in the draw stays equal.

How much BAC water for a 24 mg vial

The 24 mg stays in the vial whatever volume you add; the water only sets the concentration. This is arithmetic for reading a syringe, not a dose. For retatrutide vials, the retatrutide reconstitution calculator runs the same math. For a 20 mg retatrutide vial, see how much bac water for 20mg retatrutide, which turns each trial dose into units.

BAC water added	Concentration	Peptide in 10 units (0.1 mL)
1 mL	24 mg/mL	2.4 mg
2 mL	12 mg/mL	1.2 mg
2.4 mL	10 mg/mL	1 mg
3 mL	8 mg/mL	0.8 mg

How to reconstitute a peptide vial

Lyophilized peptides arrive as a freeze-dried powder.⁷ To use them, you mix the powder with bacteriostatic water (BAC) inside the sealed vial. Once reconstituted, keep the vial in the fridge and date the label, because no study has measured how long a mixed research peptide stays stable. Once a vial is mixed, storage matters as much as the math: does bacteriostatic water need to be refrigerated covers what the labels say before and after the bottle is opened. If bacteriostatic water is new to you, start with what is bac water, which explains what each line on its label tells you.

Wipe both rubber stoppers (peptide vial and BAC vial) with an alcohol swab and let dry.
Use a 1 mL or 3 mL syringe with a draw needle to pull the BAC water volume you entered above out of the BAC vial.
Insert the needle into the peptide vial at a slight angle so the water runs down the inside wall, not directly onto the powder. This minimizes foaming.
Inject slowly. Do not shake the vial. Gently swirl until fully dissolved.
Label the vial with reconstitution date and concentration in mg/mL.
Refrigerate. Do not freeze a reconstituted vial.

For detailed shipping and storage handling and what to do if the vial arrived warm, see the storing peptides in Vietnam's heat guide and the supplier shipping notes on each city guide. If you are weighing a single seller while you mix, our Skye Peptides review walks through a members-only store and its lab record. If the vial you are mixing is a healing peptide, our BPC-157 vs TB-500 guide lays out what each one has actually been studied for.

Picking the right BAC volume

The amount of BAC water you add does not change the total amount of peptide in the vial. It only changes the concentration, and therefore how much volume you draw per dose. Common choices:

1 mL of BAC water

More concentrated, so every draw gets smaller: a draw that reads 4 units at 2 mL reads 2 units at 1 mL, which is harder to measure. Useful only when a draw at 2 mL would not fit the syringe. Lasts the same number of weeks.

2 mL of BAC water

The default here for every vial size, and what every preset above loads. It keeps most draws in a range a U-100 syringe reads well. When a high-strength vial pushes a draw under about 5 units, the calculator flags it and tells you to draw slowly.

3 mL of BAC water

Diluted. Useful for small doses (under 200 mcg) where a more spread-out reading on the syringe reduces measurement error.¹ Check that the vial holds 3 mL before you add it.

The math is identical regardless of volume. The only practical difference is how precise your syringe reading is. If you find yourself trying to read 1 to 2 units on the syringe, dilute more.² If you are drawing close to syringe capacity, concentrate more. Any draw under about 5 units gets a draw-slowly note in the calculator above. The far end of that problem is a 100 mg GHK-Cu vial in 1 mL, where 1 mg is a single unit; our 50mg and 100mg GHK-Cu bac water guide shows how much water moves it into a readable range. The opposite problem shows up with a 1000 mg NAD+ vial, where a single amount can need more than one full 100-unit barrel; the NAD+ dosage chart lists the water volumes where that begins. A blend vial follows the same water rule, but every unit carries several peptides at once, which our GLOW blend chart breaks out per peptide for 1, 2, 3 and 5 mL.

Disclaimer: this is general education, not medical advice and not a dosing recommendation.

Reading the insulin syringe

Almost everyone in the peptide world uses U-100 insulin syringes for reconstituted peptides. The conversion is:

1 unit = 0.01 mL

100 units = 1 mL = full 1 mL syringe

So 25 units on the syringe is 0.25 mL of solution.³ The calculator above does this conversion automatically. If you ever see a result like "0.083 mL," convert to units (8.3 units) for easier reading. A full units-to-mL chart lists the common conversions. If your number is a volume, such as 0.15 mL or 1.5 mL, the mL to units guide gives the units and says which barrel size can hold it.

Smaller syringe sizes (0.3 mL and 0.5 mL) have finer graduations and are easier to read for small doses. The 1 mL syringe gives you headroom for higher-dose protocols like tirzepatide maintenance phases; for that compound specifically, the tirzepatide calculator handles the mixing math.⁹ For the growth-hormone releaser sermorelin, our sermorelin dosage chart turns its trial amounts into these same units. The amylin analogue cagrilintide gets the same treatment on the cagrilintide dosage chart, which reads each phase 2 trial amount off these marks for 5 mg and 10 mg vials. If the vial in your hand is sermorelin, the sermorelin dosage calculator loads its study amounts as buttons and counts the days a vial lasts.

Common reconstitution mistakes

Confusing mg and mcg

The single most dangerous mistake. A 250 mcg dose is 1000x smaller than a 250 mg dose.⁴ Always confirm the unit on your protocol before drawing. The calculator labels units explicitly to reduce this risk.

Shaking the vial

Shaking creates foam, which destabilizes the peptide. Gentle swirling is correct. If the powder does not dissolve immediately, give it a minute and swirl again.

Reconstituting with sterile saline instead of BAC water

Bacteriostatic water contains benzyl alcohol, which prevents bacterial growth once the vial is punctured.⁶ Sterile saline does not. A peptide reconstituted with saline must be used within hours, not weeks.¹⁰

Freezing a reconstituted vial

Freezing breaks the peptide structure. Lyophilized (dry) peptide can be frozen pre-reconstitution. Once water is added, refrigerate only.

Disclaimer: this is general education, not medical advice and not a dosing recommendation.

Where to get the vials and bacteriostatic water

Disclosure: Some links on this page are referral links. Peptides Vietnam may earn a fee at no cost to you. Editorial content is never sold.

Peptara Labs, our supply partner, lists the research compounds below along with the bacteriostatic water used to reconstitute them.

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Frequently asked questions

What is a BAC water calculator?

A BAC water calculator works out the concentration and dose volume that result from mixing a given amount of bacteriostatic water into a peptide vial. You enter the total peptide in the vial and how much BAC water you plan to add, and it returns the concentration in mg/mL, the volume per dose, and the equivalent insulin syringe units. It does the arithmetic only. It does not tell you what dose to take.

How much BAC water should I add to a 24mg retatrutide vial?

There is no single correct volume. BAC water volume is a readability choice, not a dosing choice: the total 24mg of peptide stays the same whether you add 1 mL, 2 mL, or 3 mL, only the concentration changes. For example, 24 mg in 2 mL gives 12 mg/mL, in 2.4 mL gives a round 10 mg/mL, and in 3 mL gives 8 mg/mL. Enter 24 as the vial amount in the calculator above and try a few BAC volumes to see how the concentration and syringe units shift, then match your protocol source's planned dose against that concentration.

How much BAC water for a 10mg or 20mg vial?

Same principle as any other vial size. A 10mg vial with 2 mL of BAC water gives a concentration of 5 mg/mL, and a 20mg vial with 2 mL gives 10 mg/mL. Enter your vial size above to see the exact concentration and how many insulin units a given dose from your protocol source works out to.

How many insulin units is 2mL of BAC water?

On a standard U-100 insulin syringe, 1 unit equals 0.01 mL, so 2 mL is 200 units, more than a single 1 mL syringe can hold. That figure describes the total BAC water added to the vial, not a single dose. A single dose is almost always a small fraction of that, and the calculator above converts your specific per-dose volume into units automatically.

Does adding more BAC water change the dose?

No, the total peptide mass in the vial is fixed at reconstitution and does not change no matter how much BAC water you add. Adding more water lowers the concentration, so you would draw a larger volume to reach the same dose. Adding less water raises the concentration, so the same dose is a smaller volume. The dose itself is set by your protocol source, not by the BAC water amount.

BAC water vs sterile water for reconstitution?

Bacteriostatic (BAC) water contains a small amount of benzyl alcohol as a preservative, which lets a punctured vial be drawn from more than once. Sterile water has no preservative, so a vial mixed with it should be used within hours, not weeks. For that reason BAC water is the standard choice for multi-dose peptide vials.

How many doses will my vial make?

Divide the total peptide in the vial by your per-dose amount. The calculator above does this automatically once you enter the vial size, BAC water volume, and dose, showing doses per vial alongside the concentration and syringe units. This is an arithmetic estimate assuming exact reconstitution, not a guarantee of vial yield.

How much BAC water for 100mg GHK-Cu?

The same concentration math applies regardless of compound. A 100mg GHK-Cu vial with 2 mL of BAC water works out to 50 mg/mL, or with 5 mL works out to 20 mg/mL. Enter 100 as the vial amount above and adjust the BAC water slider to see the resulting concentration and insulin units for your planned dose.

Disclaimer: this is general education, not medical advice and not a dosing recommendation.

For a second check on your numbers, try Peptara's own reconstitution calculator from our supply partner.

This is harm reduction education, not medical advice

This calculator is for educational use. Peptide protocols vary between individuals and compounds. Always cross-check with your protocol source, supplier instructions, and where possible a qualified clinician.