A peptide calculator https://peptidecalculator.store/peptide-calculator/ does one job: it converts what you want (mg or mcg) into what you draw (mL or units) after you mix your vial.

You need three pieces of information:

1. How much peptide is in the vial (ex: 5 mg or 10 mg)
2. How much bacteriostatic water you added (ex: 1 mL, 2 mL)
3. Your desired dose (ex: 250 mcg)

Step 1 - Get concentration:
Convert everything to mcg. 1 mg = 1000 mcg.
Concentration = Total mcg / mL of water added.

Example: 5 mg vial = 5000 mcg. You add 2 mL water.
5000 / 2 = 2500 mcg per mL.

Step 2 - Get dose volume:
Dose volume = Desired dose / Concentration

If you want 250 mcg: 250 / 2500 = 0.1 mL.

On a standard U-100 insulin syringe, 1 mL = 100 units, so 0.1 mL = 10 units.

If you had added only 1 mL of water, concentration would be 5000 mcg/mL, and that same 250 mcg would be 0.05 mL = 5 units. More water doesn't make it weaker — it just makes it easier to measure small doses accurately.

Always label your vial with concentration and mixing date, refrigerate after reconstitution, and use sterile technique. Check your math, storage, and dosing plan with your pharmacist or prescriber before use.