Peptide calculator

The reconstitution formula

Concentration is mass divided by volume. Take the milligrams of peptide in the vial, divide by the millilitres of bacteriostatic water added, and the result is milligrams per millilitre:

concentration (mg/mL) = peptide mass (mg) ÷ solvent volume (mL)

A 10 mg vial with 2 mL of solvent is 5 mg/mL. The same vial with 1 mL is 10 mg/mL. The peptide quantity never changes — only the volume it is dissolved in, and therefore the volume you measure out to obtain a given mass.

Why bacteriostatic water

Bacteriostatic water is sterile water containing roughly 0.9% benzyl alcohol, which inhibits bacterial growth. That is what allows a reconstituted vial to be stored and sampled more than once rather than discarded after a single use. Our guide to bacteriostatic water and peptide stability covers handling and storage in more detail.

Converting volume to pen clicks

Measuring very small volumes with a syringe is the fiddliest part of laboratory peptide work. Our reusable auto-injector pen dispenses a fixed 0.01 mL per click over a 3 mL cartridge — 300 clicks in total — so a volume converts to a whole number of clicks: 0.1 mL is 10 clicks, 0.05 mL is 5. The calculator shows this alongside the peptide mass that volume contains. See how the reusable pen works for the mechanism.

Frequently asked questions

How do you calculate peptide concentration?

Divide the mass of peptide in the vial by the volume of bacteriostatic water you add. A 10 mg vial reconstituted with 2 mL gives 10 ÷ 2 = 5 mg/mL, which is the same as 5,000 mcg/mL. The calculator above does this arithmetic and also converts a volume into the peptide mass it contains.

What is peptide reconstitution?

Reconstitution is dissolving a lyophilised (freeze-dried) peptide powder in a solvent so it becomes a liquid of known concentration. Bacteriostatic water is the usual solvent for laboratory work because the benzyl alcohol in it inhibits bacterial growth, allowing a reconstituted vial to be stored and sampled more than once.

How much bacteriostatic water should I add to a vial?

There is no single correct volume — it is a working decision, not a fixed rule. More solvent gives a lower concentration and larger measured volumes; less gives a higher concentration and smaller ones. Laboratories generally pick a volume that makes their measurements land in a range their equipment reads accurately. Our reusable pen holds 3 mL, so reconstitutions above that will not fit a single cartridge.

How many clicks is a given volume on the peptide pen?

Our reusable auto-injector pen dispenses 0.01 mL per click across a 3 mL cartridge, giving 300 clicks in total. So 0.1 mL is 10 clicks and 0.05 mL is 5 clicks. Enter a volume in the calculator and it converts it to clicks and to the peptide mass that volume contains at your concentration.

What is the difference between mg/mL and mcg/mL?

They measure the same thing at different scales. One milligram is 1,000 micrograms, so 5 mg/mL is 5,000 mcg/mL. Research literature often reports smaller peptide quantities in micrograms, which is why the calculator shows both.

Does this calculator tell me how much to use?

No. It performs unit arithmetic on the figures you enter — concentration, mass per volume, and pen clicks. It does not recommend quantities and is not guidance for use in humans or animals. All compounds we supply are for in-vitro laboratory research only.