The calculator only does the math. Check the vial label and the markings on your syringe before drawing up a dose.
Sterile water with about 0.9% benzyl alcohol, which keeps bacteria from growing after the vial stopper has been pierced. It is the usual liquid for dissolving peptides that come as a powder.
Insulin syringes are marked in units rather than millilitres, and a unit is a different volume on different syringes: on a U100 syringe 1 ml is 100 units, on a U40 syringe – 40 units. The same dose lands on a different mark, so the calculator needs to know which one you use.
Yes. The mark grows with the water: twice the water means twice the units for the same dose. Try 1, 2 or 3 ml in step 3 and keep the volume that puts your dose on a mark that is easy to read.
Divide the peptide in the vial by the dose, both in the same units: 5 mg is 5000 mcg, so a 250 mcg dose gives 20 doses. The amount of water does not change this – it only changes the mark.