Protein Concentration Calculator — mg/mL, µg/mL & µM
Calculate protein concentration from dissolved mass and volume. Enter the molecular weight to also convert to molar concentration (µM) — essential for enzyme assays, ELISA standards and dilution series.
mg
mL
Da
Mass divided by solution volume (numerically equal to g/L)
- 1
Protein concentration
5 ÷ 1 = 5Mass divided by volume; mg/mL is numerically equal to g/L. - 2
Convert to µg/mL
5 × 1000 = 5,000
How does this calculator work?
Protein concentration (mg/mL) = mass (mg) ÷ volume (mL). Multiply by 1000 for µg/mL. To convert to µM: divide mg/mL by the molecular weight in kDa and multiply by 1000. Essential for assay preparation, dilution series and equimolar reaction setup.
Formula
How this is calculated
Protein concentration is the mass of protein dissolved in a given volume. Dividing mass in milligrams by volume in millilitres gives mg/mL — the universal unit for protein solutions — which is numerically equal to g/L. Spectrophotometric assays (Bradford, BCA, absorbance at 280 nm) are calibrated to report in mg/mL. A frequent source of error is unit mismatch: 1 mg/mL = 1000 µg/mL = 1000 ng/µL, so always confirm the unit reported by your instrument before diluting.
If you know the protein's molecular weight in daltons, the calculator converts mass concentration to molar concentration in micromolar (µM). The formula is: µM = (mg/mL ÷ 1000) ÷ MW(Da) × 10⁶. For instance, 2 mg/mL of a 40 kDa protein equals 50 µM. Molar concentration is needed when setting up reactions that require equimolar ratios of protein and ligand or substrate.
This calculation assumes complete dissolution and uniform mixing. At high concentrations (typically above 20–50 mg/mL depending on the protein), partial aggregation may lower the effective solution concentration below the calculated value. Viscosity effects can also reduce pipetting accuracy at very high concentrations. The calculator does not account for these effects.
Frequently asked questions
1 mg/mL equals 1000 µg/mL, because 1 milligram is 1000 micrograms. Protein stocks are commonly quoted in mg/mL; very dilute working solutions or immunoassay standards are in µg/mL or ng/mL. Confusing these units causes 1000-fold pipetting errors, which is among the most common mistakes in protein biochemistry.
Divide the mg/mL value by the molecular weight in kDa and multiply by 1000: µM = (mg/mL / MW_kDa) × 1000. For example, 1 mg/mL of a 50 kDa protein = (1/50) × 1000 = 20 µM. Alternatively, use µM = (mg/mL × 10³) / MW(Da).
For Bradford/BCA assays, read off the standard curve (BSA standards) to get mg/mL, then enter it here to convert units. For A₂₈₀ (direct UV absorbance), use c (mg/mL) = A₂₈₀ / ε, where ε is the protein's extinction coefficient in mL·mg⁻¹·cm⁻¹ (available from databases like ProtParam or ExPASy).
Also known as
TG we-Calculate Editorial Team. (2026). Protein Concentration Calculator — mg/mL, µg/mL & µM [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/protein-concentration-calculator
TG we-Calculate Editorial Team. "Protein Concentration Calculator — mg/mL, µg/mL & µM." TG we-Calculate. 2026. https://we-calculate.com/calculator/protein-concentration-calculator.
TG we-Calculate Editorial Team, "Protein Concentration Calculator — mg/mL, µg/mL & µM," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/protein-concentration-calculator
@misc{wecalculate_protein_concentration_calculator, title = {Protein Concentration Calculator — mg/mL, µg/mL & µM}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/protein-concentration-calculator}}, year = {2026}, note = {TG we-Calculate} }
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