Peptide calculator (reconstitution arithmetic)

Two inputs and one target: how much peptide is in the vial, how much solvent you add, and how large an aliquot your protocol needs. Everything else follows from arithmetic. Results update as you type, and nothing leaves your browser — the tool has no network code at all.

No black boxes on this site. The calculator implements exactly this:

• Concentration = peptide mass ÷ solvent volume. 5 mg in 2 mL gives 2.5 mg/mL, which is 2500 µg/mL.
• Aliquot volume = target amount ÷ concentration. A 250 µg aliquot of that solution is 250 ÷ 2500 = 0.1 mL = 100 µL.
• Syringe units: a U-100 insulin syringe divides 1 mL into 100 units, so 0.1 mL reads as 10 units.
• Aliquots per vial = total mass ÷ aliquot size. 5000 µg ÷ 250 µg = 20 aliquots.

Small aliquot volumes (under ≈ 20 µL) exceed the accuracy of ordinary laboratory pipettes at the low end — if your arithmetic lands there, the fix is more dilute solution, not heroic pipetting. This is the most common arithmetic mistake in the whole domain.

Honest limits, so the tool is not over-trusted: it assumes the vial contains exactly its labeled mass of exactly its labeled compound — which is precisely what a certificate of analysis is for. Net content varies between batches; that variance is real and belongs in your uncertainty budget, not hidden in a rounding rule.