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Research Tools

⚗️ Peptide Molarity Calculator

Free laboratory calculator for research use. Results display instantly in-browser — no data is transmitted.

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About This Calculator

Cell-based and biochemical assays typically require peptide concentrations expressed in molar units — µM or nM — rather than mass-per-volume. Converting between the two requires the compound's molecular weight, which varies considerably across peptide classes (Epithalon: 390 Da; Tesamorelin: 5135 Da). This calculator handles the conversion in both directions and outputs the full range of units simultaneously.

The formula is straightforward: moles = mass (g) ÷ molecular weight (g/mol); concentration (M) = moles ÷ volume (L). This tool applies that formula and returns mM, µM, nM, mg/mL, and µg/mL in a single calculation. A reference table of molecular weights for all OL Research compounds is included so you can proceed without consulting a separate datasheet.

For in-vitro assays, most peptide working concentrations fall in the 0.1–100 µM range. Prepare a concentrated stock (e.g. 1–10 mM in DMSO or aqueous buffer) and perform serial dilutions to reach the target working concentration — use the serial dilution calculator to plan the dilution series.

Calculator

g/mol (Da)
Concentration
—µM
—nM
—mM
—mg/mL
—µg/mL

Frequently Asked Questions

How do I find the molecular weight of a research peptide?
The molecular weight appears on every Certificate of Analysis (CoA) and product datasheet. For custom or less common peptides, it can be calculated from the amino acid sequence using a peptide MW calculator, or confirmed by mass spectrometry data on the CoA.
What is the difference between µM and µg/mL?
µg/mL (micrograms per millilitre) is a mass concentration — it tells you the mass of compound per unit volume. µM (micromolar) is a molar concentration — it tells you the number of molecules per unit volume. For comparing biological activity across different compounds, molar concentration (µM or nM) is more meaningful because it accounts for molecular weight.
What concentration should I prepare as a stock solution?
A stock of 1–10 mM is typical for in-vitro work, diluted to working concentrations of 0.1–100 µM in cell culture medium. Higher stock concentrations reduce pipetting error for small working volumes. For peptides with limited solubility, prepare in DMSO (keeping final DMSO < 0.1% in assays) before aqueous dilution.