Peptide reconstitution calculator

Reconstitution maths is simple, and that is exactly why it gets fumbled. It is one division,
done while you are holding a vial in one hand, and a misplaced decimal turns 0.05 mL into 0.5 mL.
This calculator does the two conversions that actually come up: what concentration you end up with,
and what volume holds the quantity you want.

Worked example

Take a 10 mg vial and add 2 mL of bacteriostatic water. Concentration is 10 divided by 2, so
5 mg per mL, which is the same as 5000 mcg per mL.

Now suppose the protocol calls for 250 mcg. Convert to the same unit first: 250 mcg is 0.25 mg.
Then divide by concentration, 0.25 divided by 5, which gives 0.05 mL. On a U-100 insulin syringe
that is 5 units, because 100 units is 1 mL. The vial holds 2 mL, so at 0.05 mL per draw you get 40
draws out of it.

Change one input and the whole thing moves. Reconstitute that same 10 mg vial with 1 mL instead
of 2 mL and the concentration doubles to 10 mg/mL, so the same 250 mcg now sits in 0.025 mL, or
2.5 units. Same vial, same quantity, half the volume. This is the step people get wrong when they
copy a number off a forum post without checking what volume the poster reconstituted with.

The three conversions worth memorising

• 1 mg is 1000 mcg. Most mismatches are just this, applied in the wrong direction.
• On a U-100 syringe, 100 units is 1 mL. So 0.1 mL is 10 units.
• Concentration is quantity divided by volume. More water means weaker solution and larger draws.

Does it work for any peptide?

Yes, because it is arithmetic rather than anything compound-specific. If you know the mass in the
vial and the volume of solvent you added, the maths is identical whether the label says BPC-157,
semax, or anything else. What it cannot tell you is how much solvent a given compound should get, or
how stable that compound is once it is in solution. Those are properties of the material, not of the
calculation.

Things that will bite you

• Adding solvent nudges the total volume up slightly. At these volumes it is small enough that
  almost everyone ignores it, but it is an approximation rather than an exact figure.
• Reconstituted peptide is less stable than dry powder. Shelf life after reconstitution varies a
  lot by compound, and “keep it in the fridge” is not a universal answer.
• Bacteriostatic water and sterile water are not the same thing and are not interchangeable for
  every purpose. Bacteriostatic water contains benzyl alcohol.
• Insulin syringes are not all U-100. Check the barrel before trusting a unit conversion.

Research use only. Products discussed on this page are supplied for laboratory research. They are not medicines, not dietary supplements, and not for human or veterinary consumption. Nothing here is medical advice.

This calculator does unit arithmetic and nothing else. It does not recommend a
quantity, and the number it returns is not a dose. Choosing quantities for an experimental protocol
is on the researcher running it.