Free tool
Bac water
calculator.
Backwards from your syringe: pick the units you want your dose to land on, and get the exact water to add. No more awkward 7.3-unit draws.
2 ml
Concentration you get2500 mcg per ml
Vial lasts20 doses per vial
Already mixed the vial?The dosage calculator turns your numbers into syringe units
Open the dosage calculator
Why solve it backwards
Most people mix first and end up measuring 7.3 units on a tiny syringe. The smarter order: decide where you want the dose to sit — 10 or 20 units are easy to read — and let the water amount follow.
Water changes nothing about the dose itself. A 250 mcg dose is 250 mcg whether it occupies 5 units or 25. More water simply spreads the same vial across more units, which makes small doses easier to draw accurately.
The sweet spot
Keep each dose between 5 and 50 units and total water between 1 and 3 ml. Below that range measurement errors grow; above it the vial gets crowded and doses stop fitting a small syringe.
Your pharmacy label overrides any general rule. This tool is math, not a prescription.