For laboratory and in-vitro research only. Not for human or veterinary use. Not medical advice.

Lab tools

Peptide lab calculator: stock solutions, molarity and dilutions

Bench math for researchers working with lyophilized peptides. Make a stock solution, convert to molar concentration, plan working dilutions for in-vitro assays and split stock into aliquots. Check molecular weight against your batch COA.

Stock solution concentration

Peptide mass in the vial plus solvent volume gives stock concentration.

Compound (sets molecular weight)

Peptide mass in vial (mg)

Solvent volume (mL)

Molecular weight (g/mol)

Solvent

Stock concentration

2.50 mg/mL

Same, in µg/µL

2.50 µg/µL

Molar concentration

1.761 mM

Solvent choice depends on peptide solubility. Check the supplier's solubility note and COA.

Mass needed for a target molarity

How much peptide to weigh for a solution of a given molar concentration and volume.

Compound

Molecular weight (g/mol)

Final volume (mL)

Target concentration

Unit

Mass to weigh

1.420 mg

In µg

1419.5 µg

Moles in solution

1.000 µmol

mass (g) = concentration (mol/L) × volume (L) × MW (g/mol)

Working dilution

Volume of stock to add to reach a working concentration (C1V1 = C2V2). Use the same unit for both concentrations.

Stock concentration (C1)

Target concentration (C2)

Final volume (V2)

Volume unit

Stock to add (V1)

10.00 µL

Diluent / medium to add

990.00 µL

Dilution factor

1 : 100

C1 × V1 = C2 × V2

Serial dilution series

Concentration at each step for dose-response curves in cell or enzyme assays.

Starting concentration

Unit

Fold per step

Number of steps

Volume per well/tube (µL)

Transfer per step

50.0 µL into 100 µL diluent

Step	Concentration

Aliquot planner

Split stock into single-use aliquots to avoid repeated freeze-thaw cycles.

Total stock volume (mL)

Aliquot size (µL)

Stock concentration (mg/mL)

Number of aliquots

Peptide per aliquot

125.0 µg

Leftover volume

0 µL

Typical practice: store lyophilized powder at −20 °C, label aliquots with lot number and date, thaw once.

Compound reference for lab researchers

Molecular weights and the preclinical research areas each compound is studied in. Verify MW against your batch COA; salt forms and modifications change it.

Compound	MW (g/mol)	Common vial sizes	Studied in (preclinical / in-vitro)	Status on this site

Excluded from vendor promotion on this site: GLP-1 and incretin analogues (semaglutide, tirzepatide, retatrutide, cagrilintide, survodutide, mazdutide), PT-141, tesamorelin, ipamorelin, SS-31, gonadorelin and other compounds named in 2026 FDA warning letters to peptide sellers.

Questions researchers ask

Why does molecular weight matter?

Molar concentration depends on it. Acetate or TFA salt forms add mass, so the figure on the batch COA is the one to use.

Which solvent should I use?

It depends on the sequence. Many peptides dissolve in sterile water; basic peptides often need dilute acetic acid; hydrophobic ones may need a small amount of DMSO before dilution in buffer. Follow the supplier's solubility data.

Does this calculator give doses?

No. It handles solution chemistry for laboratory work only. It does not calculate doses, syringe units or anything intended for administration to people or animals.

Research use only. Compounds referenced here are not approved by the FDA, MHRA or EMA for human use. This tool performs laboratory calculations and is not medical, dosing or treatment guidance.