This free peptide calculator does the three calculations everyone running peptides needs: reconstitution (how much bacteriostatic water to mix, and how many insulin-syringe units equal your dose), GLP-1 dosing for retatrutide, tirzepatide and semaglutide with full titration schedules, and BPC-157 / TB-500 dosing by fixed amount or bodyweight. Enter your vial strength and water volume and it returns the exact line to draw to on a U-100, U-50 or U-30 syringe, your vial concentration, and how many doses your vial holds. You can email yourself the results so the numbers are on your phone when you are standing at the fridge with a syringe.
How peptide reconstitution math works
Every peptide calculation comes down to one number: concentration. Divide the milligrams of peptide in your vial by the milliliters of bacteriostatic water you add, and you get mg per ml. Your dose in ml is simply your desired dose divided by that concentration. Multiply ml by 100 and you have insulin-syringe units on a standard U-100 syringe.
Example: a 10 mg vial mixed with 2 ml of bacteriostatic water gives 5 mg/ml (5,000 mcg/ml). A 250 mcg dose is 0.05 ml, which is the 5-unit line on a U-100 insulin syringe, and the vial holds 40 doses.
How much bacteriostatic water should you add?
There is no single right answer. More water means a lower concentration and a bigger, easier-to-measure draw; less water means smaller injection volumes. The practical rule: pick a volume that puts your typical dose between 5 and 30 units on the syringe. Below 5 units, small measurement errors become a big percentage of your dose. Above the syringe capacity you physically cannot draw it. The calculator flags both cases automatically.
GLP-1 dosing: retatrutide, tirzepatide, semaglutide
GLP-class compounds are dosed weekly in milligrams and titrated up over months. The calculator includes the standard escalation schedules (retatrutide from 2 mg, tirzepatide from 2.5 mg, semaglutide from 0.25 mg) and converts every phase into syringe units for your specific vial and water volume. Jon covers the strategy in depth in his retatrutide sweet-spot protocol: the right dose is the lowest one that still lets you eat protein and train hard, not the highest one you can tolerate.
BPC-157 and TB-500 dosing
The healing peptides are dosed in micrograms, either as a fixed amount (BPC-157 commonly 250 to 500 mcg, TB-500 commonly 500 mcg to 2 mg loading) or scaled per kilogram of bodyweight. The calculator supports both bases plus the popular BPC/TB blend vials. For how these fit a recovery-first protocol, see Jon’s summer cut sweet-spot breakdown.
Frequently asked questions
How many units is 250 mcg on an insulin syringe?
It depends entirely on your concentration. With a 10 mg vial in 2 ml of water (5,000 mcg/ml), 250 mcg is 5 units on a U-100 syringe. With the same vial in 1 ml, it is 2.5 units. Run your exact numbers in the calculator above.
What syringe should I use for peptides?
Most people use U-100 insulin syringes (100 units = 1 ml) with a 29 to 31 gauge needle. U-50 and U-30 syringes measure smaller volumes more precisely; the calculator converts to all three.
How long does a reconstituted peptide last?
Refrigerated and mixed with bacteriostatic water, most peptides remain stable for 3 to 8 weeks depending on the compound. Always store reconstituted vials in the fridge and out of light.
Is this medical advice?
No. The calculator performs arithmetic for educational and research purposes only. Consult a licensed healthcare provider before using any peptide.