Reconstitution · any peptide
Peptide calculator
This peptide calculator turns a vial of powder into syringe units. Put in the vial strength, the water you added and the dose you want.
The calculator
Step 1 of 4
Sample numbers are loaded to show how the calculator works. Replace them with the vial, water, dose and syringe values you are using.
amount printed on the vialmg- how much water you addedmL
A U-100 syringe holds 1 mL, so 2 mL of water goes in as 2 full draws.
- Dose to drawenter the dose you want to convert
This vial holds 10 mg in total.
- Syringe typematch the label on your syringe
U-100 insulin syringe · 1 mL · lines every 2 units · 1 unit = 0.01 mL
Sample result
20.0units
20.0 units on a U-100 insulin syringe · 1 mL · lines every 2 units, which is 0.20 milliliters. The draw lands on a syringe line.
10 mg ÷ 2 mL = 5.00 mg/mL
→ 50 mcg/unit · 1 mg = 0.200 mL = 20.0 units
→ 50 mcg/unit · 1 mg = 0.200 mL = 20.0 units
Show the math and syringe details
Can this syringe show the result clearly?
Want an easier syringe number?
Three quick steps
How to use this peptide calculator
- STEP 1Copy the vial
- STEP 2Add water and dose
- STEP 3Read the syringe
Calculators for specific compounds
The main calculator works with any peptide. Choose a compound below to load its common vial sizes and open the evidence guide beside it.
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Browse 26 more peptide calculators
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Example mix & evidence
Which calculator tab should I use?
Start with the numbers you already have. Each tab answers a different question.
Start with
The vial strength, water and dose
Start with
The vial strength, water and syringe units
Start with
The mixed vial, dose and weekly schedule
The Dose build-up tab appears only when we have a sourced half-life. It is currently available for Tirzepatide, Semaglutide, Liraglutide. Other calculators leave it out instead of using an unsupported number.
What does one syringe unit contain?
It depends on how much peptide and water are in the vial. Use the calculator for your own numbers. Open the table only if you want to compare many common mixtures at once.
Open the full vial-and-water table
◆ 30 distinct concentrationsfrom 48 mixes · 0.33–100 mg/mL
| Concentration | One U-100 or U-50 unit | One U-40 unit | Mixes that give it |
|---|---|---|---|
| 0.33 mg/mL | 3.3 mcg | 8.3 mcg | 1 mg ÷ 3 mL |
| 0.40 mg/mL | 4.0 mcg | 10.0 mcg | 1 mg ÷ 2.5 mL |
| 0.50 mg/mL | 5.0 mcg | 12.5 mcg | 1 mg ÷ 2 mL |
| 0.67 mg/mL | 6.7 mcg | 16.7 mcg | 1 mg ÷ 1.5 mL · 2 mg ÷ 3 mL |
| 0.80 mg/mL | 8.0 mcg | 20.0 mcg | 2 mg ÷ 2.5 mL |
| 1.00 mg/mL | 10.0 mcg | 25.0 mcg | 1 mg ÷ 1 mL · 2 mg ÷ 2 mL |
| 1.33 mg/mL | 13.3 mcg | 33.3 mcg | 2 mg ÷ 1.5 mL |
| 1.67 mg/mL | 16.7 mcg | 41.7 mcg | 5 mg ÷ 3 mL |
| 2.00 mg/mL | 20.0 mcg | 50.0 mcg | 1 mg ÷ 0.5 mL · 2 mg ÷ 1 mL · 5 mg ÷ 2.5 mL |
| 2.50 mg/mL | 25.0 mcg | 62.5 mcg | 5 mg ÷ 2 mL |
| 3.33 mg/mL | 33.3 mcg | 83.3 mcg | 5 mg ÷ 1.5 mL · 10 mg ÷ 3 mL |
| 4.00 mg/mL | 40.0 mcg | 100.0 mcg | 2 mg ÷ 0.5 mL · 10 mg ÷ 2.5 mL |
| 5.00 mg/mL | 50.0 mcg | 125.0 mcg | 5 mg ÷ 1 mL · 10 mg ÷ 2 mL · 15 mg ÷ 3 mL |
| 6.00 mg/mL | 60.0 mcg | 150.0 mcg | 15 mg ÷ 2.5 mL |
| 6.67 mg/mL | 66.7 mcg | 166.7 mcg | 10 mg ÷ 1.5 mL · 20 mg ÷ 3 mL |
| 7.50 mg/mL | 75.0 mcg | 187.5 mcg | 15 mg ÷ 2 mL |
| 8.00 mg/mL | 80.0 mcg | 200.0 mcg | 20 mg ÷ 2.5 mL |
| 10.00 mg/mL | 100.0 mcg | 250.0 mcg | 5 mg ÷ 0.5 mL · 10 mg ÷ 1 mL · 15 mg ÷ 1.5 mL · 20 mg ÷ 2 mL · 30 mg ÷ 3 mL |
| 12.00 mg/mL | 120.0 mcg | 300.0 mcg | 30 mg ÷ 2.5 mL |
| 13.33 mg/mL | 133.3 mcg | 333.3 mcg | 20 mg ÷ 1.5 mL |
| 15.00 mg/mL | 150.0 mcg | 375.0 mcg | 15 mg ÷ 1 mL · 30 mg ÷ 2 mL |
| 16.67 mg/mL | 166.7 mcg | 416.7 mcg | 50 mg ÷ 3 mL |
| 20.00 mg/mL | 200.0 mcg | 500.0 mcg | 10 mg ÷ 0.5 mL · 20 mg ÷ 1 mL · 30 mg ÷ 1.5 mL · 50 mg ÷ 2.5 mL |
| 25.00 mg/mL | 250.0 mcg | 625.0 mcg | 50 mg ÷ 2 mL |
| 30.00 mg/mL | 300.0 mcg | 750.0 mcg | 15 mg ÷ 0.5 mL · 30 mg ÷ 1 mL |
| 33.33 mg/mL | 333.3 mcg | 833.3 mcg | 50 mg ÷ 1.5 mL |
| 40.00 mg/mL | 400.0 mcg | 1,000.0 mcg | 20 mg ÷ 0.5 mL |
| 50.00 mg/mL | 500.0 mcg | 1,250.0 mcg | 50 mg ÷ 1 mL |
| 60.00 mg/mL | 600.0 mcg | 1,500.0 mcg | 30 mg ÷ 0.5 mL |
| 100.00 mg/mL | 1,000.0 mcg | 2,500.0 mcg | 50 mg ÷ 0.5 mL |
Concentration = vial mg ÷ water mL. Mass per unit = concentration × one syringe unit, which is 0.01 mL on a U-100 or U-50 and 0.025 mL on a U-40. That is why one column serves two syringe types and the third differs. No dose is implied by any row — these are properties of a mixed vial, before anyone decides what to draw.
U-100 vs U-50 vs U-40 syringes
U-100 and U-50 use the same amount of liquid per unit. A U-40 unit holds 2.5 times more. Always choose the syringe you actually have before using the unit result.
Compare the three syringe types
| Syringe | 1 unit | Capacity | Small lines | Numbered every | 0.25 mL reads as |
|---|---|---|---|---|---|
| U-100 | 0.01 mL | 100 u · 1 mL | 50 · one every 0.02 mL | 10 u | 25 u |
| U-50 | 0.01 mL | 50 u · 0.5 mL | 50 · one every 0.01 mL | 5 u | 25 u |
| U-40 | 0.025 mL | 40 u · 1 mL | 40 · one every 0.025 mL | 5 u | 10 u |
The syringe drawn in the calculator uses the same line spacing shown here.
Units to dose at 5.00 mg/mL
This example uses 10 mg into 2 mL and one U-100 unit carries 50 mcg. For another mix, use the Check syringe units tab. These are examples, not suggested doses.
Open the U-100 conversion table
| U-100 units | Volume | Mass (mcg) | Mass (mg) |
|---|---|---|---|
| 10 u | 0.10 mL | 500 mcg | 0.5 mg |
| 20 u | 0.20 mL | 1,000 mcg | 1 mg |
| 30 u | 0.30 mL | 1,500 mcg | 1.5 mg |
| 40 u | 0.40 mL | 2,000 mcg | 2 mg |
| 50 u | 0.50 mL | 2,500 mcg | 2.5 mg |
| 60 u | 0.60 mL | 3,000 mcg | 3 mg |
| 70 u | 0.70 mL | 3,500 mcg | 3.5 mg |
| 80 u | 0.80 mL | 4,000 mcg | 4 mg |
| 90 u | 0.90 mL | 4,500 mcg | 4.5 mg |
| 100 u | 1.00 mL | 5,000 mcg | 5 mg |
Want to check the math?
You do not need these formulas to use the calculator. They are here so you can check every step.
- Concentration — vial strength divided by the water you added: mg ÷ mL = mg/mL.
- Volume — the dose divided by that concentration: mg ÷ (mg/mL) = mL. A dose in mcg is divided by 1,000 first.
- Units — the volume divided by what one syringe unit holds: mL ÷ 0.01 for U-100, mL ÷ 0.025 for U-40. This is why the calculator asks for the syringe type.
- Rounding gap — the exact draw against the nearest syringe line: |exact − nearest line| ÷ exact × 100 = % difference. If the answer falls between two lines, the calculator shows both instead of silently rounding it.
Worked end to end: 10 mg in 2 mL is 5.00 mg/mL. A 1 mg dose is 1 ÷ 5.00 = 0.20 mL, and on a U-100 syringe that is 0.20 ÷ 0.01 = 20 units — the 20-unit line, so nothing to round.
That sum is small, and getting it wrong is the single most-reported problem with the two biggest drugs people draw from a vial. The study behind that, read from FDA reports.
Questions people ask about peptide calculators
How much bacteriostatic water should I add to a peptide vial?
That is your choice, and it changes the reading rather than the drug. The vial holds a fixed amount of powder either way. More water spreads the same dose across a longer draw, which is easier to read; less water makes the draw smaller and harder to line up. Pick a volume that puts your dose on a numbered line. The calculator does that part: when a draw falls between two lines, it lists water volumes that put the same dose on a line, best first, and one tap applies one.
Does adding more bacteriostatic water make the dose stronger?
No. The vial holds a fixed amount of powder, so more water just spreads it thinner. Double the water and the same dose takes twice the liquid and twice the syringe units — the same amount of peptide still leaves the vial. A 10 mg vial is 10.00 mg/mL in 1 mL and 5.00 mg/mL in 2 mL.
Someone told me syringe units. How much peptide is that?
On its own, none — a unit count is a line on a syringe, not an amount of peptide. It becomes an amount once you know two more things: how the vial was mixed, and which syringe the number was written for. Put all three into the Check syringe units tab. It reports the amount, and it reports what the same count would carry on each of the other two syringe types, so you can see whether the missing word matters.
Why does the same unit count mean different amounts?
Because a unit describes a line on one particular syringe. U-100 and U-50 syringes use the same 0.01 mL per unit, so those two always agree. A U-40 unit is 0.025 mL, so it holds two and a half times as much liquid. The same unit number therefore carries 2.5× the peptide on a U-40. Nothing about the vial changed; only the ruler did.
What size syringe should I get for peptides?
That is a choice about reading, not about the peptide. A longer draw is usually easier to see, and the same liquid produces 2.5 times as many units on a U-100 as on a U-40. Most people drawing peptides use a U-100 insulin syringe for that reason. The calculator works with whichever you have, and the table above shows what one unit means on each.
What if my peptide is not in your list?
It still works. The math only needs four things — vial strength, water, dose and syringe type — and none of them depend on which peptide is in the vial. Leave the selector on Enter my own values and type the numbers off your label. Picking a listed compound only fills in its usual vial sizes as shortcuts.
Browse 7 more questions
What syringe should I use for a peptide dose?
Use whichever syringe you actually have. Tell the calculator which one it is, because a unit count means nothing without it. A longer draw is usually easier to see. The same liquid uses 2.5 times fewer units on a U-40 than on a U-100.
What does units mean on an insulin syringe?
A unit is one step on that particular syringe, not a fixed amount of peptide. One unit is 0.01 mL on a U-100 and 0.025 mL on a U-40. How much peptide a unit carries depends entirely on how you mixed the vial. That is why the table above lists mcg per unit for each mix.
Why does my draw fall between two syringe lines?
Because a U-100 syringe is printed one unit at a time, and the answer is not always a whole number. A draw of 16.67 units falls between the 16- and 17-unit lines. How much that matters depends on the size of the draw: one unit out of 50 is 2%, while one unit out of 5 is 20%. The calculator shows the exact answer, the nearest line and the difference, then suggests water volumes that land the same dose on a line.
How long does a reconstituted vial last?
Two clocks run at once: the vial runs out, or the mixed vial passes the point where it should be thrown away. The vial-life tab counts the first. The second is not math, and we never invent it — where one of our compound guides carries a sourced figure, picking that compound shows it with its source, and where it does not, the calculator says so. For a specific vial, the pharmacy that dispensed it is the one to ask.
Can sterile water be used instead of bacteriostatic water?
They are different products, and the labeling on each governs. Bacteriostatic water contains a preservative, usually benzyl alcohol, which is what lets a vial be punctured more than once. Sterile water for injection has no preservative and is labeled single-dose. That is also why swapping one for the other changes how long a mixed vial keeps. This page does the math and nothing more.
What if the dose is too small to measure?
The calculator flags any draw under two units, because one syringe line is a large part of such a small draw. More water spreads the same dose across a longer draw. A U-100 also shows the same liquid across 2.5 times as many units as a U-40.
Can I share the exact setup I calculated?
Yes. Every input is written into the page address as you change it. Copy the link and it reproduces the vial strength, water, dose, unit, syringe type, mode and compound exactly. Nothing is stored on a server — the link carries all of it.