Pick the vial, the water you added and the dose. Get the exact draw in units for the syringe in your hand.
Draw to30.0units0.30 mL
Step 1 of 4
1How many mg are in your vial?
Vial strengthamount printed on the vial
2How many mL of water did you add?
Bacteriostatic water addedhow much water you added
3What dose do you want to convert?
Target doseenter the dose you want to convert
This vial holds 1.75 mg in total.
4Which syringe are you using?
Syringe typematch the label on your syringe
U-100 insulin syringe · 1 mL · lines every 2 units · 1 unit = 0.01 mL
Draw to
30.0units
0.30 mL · 5.83 mg/mL · 58 mcg per unit · 1 doses per vial
30.0 units on a U-100 insulin syringe · 1 mL · lines every 2 units, which is 0.30 milliliters. The draw lands on a syringe line.
Easy to read on this syringe. Draw to the 30-unit line. No rounding is needed.
1.75 mg ÷ 0.3 mL = 5.83 mg/mL → 58 mcg/unit · 1.75 mg = 0.300 mL =30.0 units
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Show the math and syringe details+
Can this syringe show the result clearly?
Easy to read on this syringe.30.0 u is exactly the 30-unit line on a U-100 — no rounding error at all.
Want an easier syringe number?
This setup is already easy to read. Changing the water between 0.5 and 3 mL would not put 1.75 mg closer to a line on this U-100 syringe.
Adding more water makes the mixture less concentrated, so the same dose uses more syringe units. It does not change how much peptide is in the vial.
This setup is in the address bar — every input is part of the link.
Educational math, not medical advice — dosing decisions belong to a licensed clinician. The tabs above also plan a schedule week by week and count how many doses one vial holds.
How to use the calculator
STEP 1
Enter the amount in the vial
Use the total amount printed on the vial, in mg.
STEP 2
Enter the water you added
Use the amount of water added to that vial, in mL.
STEP 3
Enter the dose you want to convert
Choose mg or mcg, then match the result to your syringe.
PT-141 is the development code for bremelanotide. It acts on melanocortin receptors in the brain, rather than on blood flow the way the erectile-dysfunction pills do. It is bought mostly by men, for erections and desire.
That is the one group its label rules out. Vyleesi was approved in 2019 for premenopausal women with low sexual desire. The same label excludes postmenopausal women, and use to improve sexual performance. In the trials behind it, 18% of participants stopped because of a reaction.
Examples using a 1.75 mg PT-141 vial
Each row starts with the same 1.75 mg vial and changes only the amount of water. More water makes the mixture less concentrated, so the same dose uses more syringe units.
◆ How the water amount changes the resultdose used: 1.75 mg
For a 1.75 milligram vial: bacteriostatic water added, resulting concentration, micrograms per U-100 unit, and the draw for a 1.75 mg dose.
Water added
Concentration
Per U-100 unit
Draw for 1.75 mg
Nearest syringe line
0.3 mL
5.83 mg/mL
58.3 mcg
30.0 u · 0.300 mL
exactly 30 u
The vial, water and dose shown here are the calculator’s starting example for PT-141. Replace them with your own values. Every result in the table is calculated from those inputs.
Drawn from once a week at 1.75 mg, a 1.75 mg vial yields 1 doses — about 1.0 weeks of supply. No cited source says how long the mixed vial keeps, so no storage window is shown.
One vial size, one water volume, one answer
There is one documented vial size and one mixing volume, so only one concentration is shown. The full dose uses the whole vial.
3Open the mixing details — 3 notes
The whole vial empties in one draw
The approved product is a filled autoinjector holding this amount, ready to use, with no mixing anywhere in its label. A powder vial of the same amount is not that product. But the quantity matches, and it means the vial goes in one pull.
So the questions that dominate other pages here barely apply. Nothing is left to store, nothing is rationed, and how long a mixed vial keeps stops being the deciding factor it is elsewhere.
A small fill leaves a large residue
The mixing volume on this page is the smallest any preset on the site produces. Whatever clings to the glass and sits in the needle hub is a fixed amount. On a small fill that is a much bigger share of the total than on a large one.
When the full vial is one dose, liquid left behind means receiving slightly less than the full amount. The calculator cannot measure that residue.
The mistake: planning it like a schedule
The labeled use is occasional and timed to an event, with a cap on how often it may repeat. It is not a weekly course.
The vial-life mode assumes a repeating interval, because most compounds have one. Feed this compound into that shape and you get a tidy answer to a question it does not have.
The only quantity in this group that comes off a label
PT-141 is the development code for bremelanotide, and bremelanotide is approved. So this is the one page here whose number is a label instruction rather than a trial arm, a circulating range or nothing at all. It also carries the strangest presets on the site, because the approved product is never mixed.
4Read the supporting evidence — 4 supporting notes
The water volume on this page is the label’s own fill
The approved product arrives as a single-dose autoinjector holding a ready-made solution. There is no powder in it, and no mixing step anywhere in its label.
A fixed amount, with no ladder anywhere in the label
Most approved medicines on this site come with a titration schedule that climbs over weeks. This one does not. The label names a single amount, taken as needed, with no step up and no step down.
A published half-life, and still no accumulation section
This is the one record in the group whose source does state a half-life. The label gives a mean terminal figure with a range around it.
The label bounds it three ways, and the tool models none of them
Every limit is on frequency rather than on the amount. At most one dose in a day. A monthly ceiling above that. And a point, counted in weeks, at which the label says to stop when nothing has improved.
Units to dose at 5.83 mg/mL
Mix 1.75 mg into 0.3 mL and one U-100 unit carries 58.3 mcg. The table shows how much peptide is in each numbered syringe line. These are conversion examples, not suggested doses.
10Open the unit conversion table — 10 rows
Numbered U-100 syringe lines converted to volume and mass at 5.83 milligrams per milliliter.
U-100 line
Volume
Mass (mcg)
Mass (mg)
10 u
0.10 mL
583 mcg
0.583 mg
20 u
0.20 mL
1,167 mcg
1.167 mg
30 u
0.30 mL
1,750 mcg
1.75 mg
40 u
0.40 mL
2,333 mcg
2.333 mg
50 u
0.50 mL
2,917 mcg
2.917 mg
60 u
0.60 mL
3,500 mcg
3.5 mg
70 u
0.70 mL
4,083 mcg
4.083 mg
80 u
0.80 mL
4,667 mcg
4.667 mg
90 u
0.90 mL
5,250 mcg
5.25 mg
100 u
1.00 mL
5,833 mcg
5.833 mg
How the math works
Concentration — divide the amount in the vial by the water you added: mg ÷ mL = mg/mL. This tells you how many mg are in each mL.
Volume — the dose divided by that concentration: dose ÷ (mg/mL) = mL.
Units — on a U-100 syringe one unit is 0.01 mL, so mL × 100 = units. A U-40 unit is 0.025 mL, so the wrong barrel is a 2.5× error. That is why the calculator asks which one you have.
Rounding gap — the exact draw against the nearest syringe line: |exact − nearest line| ÷ exact × 100 = % difference.
Medically reviewed by Jennifer Montecillo, MD · non-practicing medical reviewer·Reviewed 2026-08-12·open the primary sources
Useful guides for this calculation
The math is only one part of the question. These guides cover the compound, published doses, side effects, mixing steps and supplies.
The approved product is never mixed. Vyleesi arrives as a filled autoinjector holding 1.75 mg in 0.3 mL of solution, and nothing in its label is reconstituted.
This page mirrors that fill, so its one preset is 1.75 mg in 0.3 mL, or 5.83 mg/mL. At that strength the whole vial is a 30 unit draw. Any other volume is your choice rather than a label’s.
How many units of PT-141 should I take?
The label sets one fixed quantity, 1.75 mg, which on this page’s mixing is 30 units. It caps use at one dose in 24 hours and advises against more than 8 doses a month.
That quantity belongs to one group: premenopausal women with acquired, generalized hypoactive sexual desire disorder. The label rules the drug out for men, for postmenopausal women, and for enhancing sexual performance. A powder vial matching the milligrams is still not the approved product.
Where is the best place to inject PT-141 peptide?
The label names two places and ranks neither: under the skin of the abdomen, or of the thigh. It sets the timing at least 45 minutes before anticipated sexual activity.
No published comparison puts one site above the other, so nobody can honestly call one best. The label does rule the drug out entirely in uncontrolled high blood pressure or known heart disease.
How much water to reconstitute 10 mg of peptide?
For any peptide the shape is identical: pick a volume, and the strength is the milligrams divided by it. 10 mg in 1 mL is 10 mg/mL, so one U-100 unit holds 100 micrograms. 2 mL halves that to 50.
10 mg is also nearly six times what this page’s vial holds. That gap matters more than the arithmetic. A vial holding one labeled dose and a vial holding many are different objects with different questions.
1primary source, each with the day we read it — open the documents used on this page