Peptide Calculator
Work out peptide reconstitution and the exact insulin-syringe unit mark to draw to.
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What is this?
A Peptide Calculator works out how far to draw an insulin syringe once a lyophilised peptide has been reconstituted, from the vial strength, the volume of bacteriostatic water added and the dose wanted. It is reconstitution arithmetic, not medical advice.
How to Use the Peptide Calculator
A peptide calculator works out how far to draw an insulin syringe once a lyophilised peptide has been reconstituted. Three numbers decide it: how much peptide is in the vial, how much bacteriostatic water you added, and the dose you want.
The step people get wrong is the last one. Insulin syringes are U-100, so the numbers printed on the barrel are insulin units and 100 of them make 1 mL. A 0.3 mL syringe reads 0 to 30 and a 1 mL syringe reads 0 to 100, but the individual marks are the same size on both.
This is arithmetic only. It is not medical advice and says nothing about whether a dose is appropriate or safe.
1. Enter the Vial Strength
The milligrams of peptide in the vial, printed on the label. Common sizes are 2, 5, 10 and 15mg, and there are one-tap buttons for the usual values.
2. Enter the Water You Added
The volume of bacteriostatic water used to reconstitute. This is entirely your choice and it does not change how much peptide is in the vial - only how dilute it is.
3. Enter Your Dose
The amount per injection, in micrograms or milligrams. Doses are usually quoted in micrograms, and 1 mg is 1000 mcg.
4. Pick Your Syringe
0.3 mL (30 units), 0.5 mL (50 units) or 1 mL (100 units). All are U-100, so the choice only affects whether your dose fits on the barrel.
5. Draw to the Mark
The result shows the unit mark to draw to, with a diagram of the barrel. It also warns if the dose will not fit the syringe or is too small to measure accurately.
Key Formulas Used in the Calculator
Concentration
Concentration (mcg/mL)=Water (mL)Vial (mg)×1000
5 mg in 2 mL is 5000 mcg over 2 mL, which is 2500 mcg per mL. Adding more water lowers the concentration but never changes the total peptide in the vial.
Volume to Draw
Volume (mL)=Concentration (mcg/mL)Dose (mcg)
A 250 mcg dose from a 2500 mcg/mL solution is 250 ÷ 2500 = 0.1 mL.
Syringe Units
Units=Volume (mL)×100
Insulin syringes are U-100, so 1 mL is 100 units. That 0.1 mL is 10 units - the same 10 mark on a 0.3 mL, 0.5 mL or 1 mL syringe.
Doses per Vial
Doses=Dose (mcg)Vial (mcg)
A 5 mg vial is 5000 mcg, so at 250 mcg per dose it yields 20 doses. This does not depend on how much water you added.
Benefits
Gives the exact unit mark to draw to, not just a volume
Shows the concentration in both mcg/mL and mg/mL
Warns when a dose will not fit the chosen syringe
Warns when a dose is too small to measure accurately
Catches a dose larger than the whole vial - usually a mcg and mg mix-up
Shows how many doses a vial yields
Draws the syringe barrel with the draw point marked
When & Where to Use
Working out the draw for a freshly reconstituted vial
Deciding how much water to add for easy-to-read doses
Checking a calculation before drawing
Seeing how many doses a vial will provide
Converting a dose given in milligrams into syringe units
Choosing between a 0.3, 0.5 and 1 mL syringe
Who Should Use This Calculator
The Peptide Calculator is for researchers and clinicians handling reconstituted peptides who need the reconstitution arithmetic checked. It is not a dosing guide and does not replace professional medical direction.
Tips to Get the Best Deal
Adding more water makes small doses easier to draw accurately
The water volume never changes how much peptide the vial holds
1 mg is 1000 mcg - a mix-up here is the most common error
Draw to a whole unit mark where you can rather than between marks
A 0.3 mL syringe has the same mark spacing as a 1 mL one, just fewer of them
Check the vial label rather than assuming a standard strength
Reconstituted peptides need refrigeration and have a limited life
Frequently Asked Questions (FAQs)
How do you calculate a peptide dose?
Concentration = vial mg x 1000 / water mL, giving mcg per mL. Volume = dose mcg / concentration. Units = volume x 100, because insulin syringes are U-100. So 250 mcg from 5 mg in 2 mL is 0.1 mL, or 10 units.
What does U-100 mean?
It means 100 insulin units per millilitre. The numbers on an insulin syringe are units, not millilitres, so 100 units is 1 mL and 20 units is 0.2 mL. All standard insulin syringes are U-100.
Does a 0.3 mL syringe measure differently from a 1 mL one?
No. Both are U-100 and the marks are the same size; the smaller barrel simply has fewer of them. 20 units means 0.2 mL on either. The only difference is the largest dose that fits.
How much bacteriostatic water should I add?
It is your choice and does not change how much peptide the vial holds. More water spreads the same dose over more syringe units, which makes small doses much easier to draw accurately.
Why does it say my dose is too small to measure?
Because it lands within the first couple of marks on the barrel, where a small misread is a large proportional error. Reconstituting with more water fixes it by making the solution more dilute.
How many doses will a vial give?
Divide the vial contents in micrograms by the dose in micrograms. A 5 mg vial is 5000 mcg, so 250 mcg doses give 20. The water volume makes no difference.
Is this medical advice?
No. It performs reconstitution arithmetic and nothing more. Research peptides are not approved medicines in most jurisdictions, and anything injected should be directed by a qualified clinician.
Pro Tips
Adding more water makes small doses easier to draw accurately.
The water volume never changes how much peptide the vial holds.
1 mg is 1000 mcg - a mix-up here is the most common error.
A 0.3 mL syringe has the same mark spacing as a 1 mL one, just fewer marks.
Draw to a whole unit mark where possible rather than between marks.
Arithmetic only - not medical advice or a dosing recommendation.