← All calculators

Protein Concentration from A280

Beer–Lambert from the extinction coefficient and MW, or the E1% mode (e.g. IgG) — mg/mL, µM and total yield. The same math as the Excel workbook, live in your browser.

What this is for: Protein concentration from an A280 reading — from the extinction coefficient and MW, or the E1% mode (e.g. IgG).

The formula: mg/mL = A280 ÷ (ε × path length) × MW × dilution factor

How to use:

  1. Enter the shared inputs: the blank-corrected A280 reading, the cuvette / path length (cm) and the dilution factor — if the prep is turbid, correct the reading for light scattering first (subtract A320).
  2. For Mode A, enter the molar extinction coefficient ε and the molecular weight, and read the concentration in mg/mL and µM.
  3. For Mode B, enter E (the A280 per 1 mg/mL at 1 cm) and read the concentration in mg/mL.
  4. Enter the solution volume (mL) to get the total protein by Mode A (mg).

Shared Inputs

Correct the reading for light scattering if the prep is turbid (subtract A320).

Mode A — Extinction Coefficient

From the molar extinction coefficient and MW (Beer–Lambert).

Concentration (mg/mL)
Concentration (µM)
Total protein by Mode A (mg)

Mode B — E1% (A280 of 1 mg/mL Solution)

From E1% — the A280 of a 1 mg/mL solution (e.g. ~1.4 for a typical IgG).

Concentration (mg/mL)
Prefer to work offline or keep a copy? The download link is right below.
Download the Protein Concentration from A280 workbook (.xlsx)
Notes & limits (from the workbook): Mode A: from the molar extinction coefficient and MW. Mode B: from E1% — the A280 of a 1 mg/mL solution (e.g. ~1.4 for a typical IgG). Correct the reading for light scattering if the prep is turbid (subtract A320).