Protein Concentration Calculator
Convert protein concentration between mg/mL and molarity using molecular weight, then estimate nmol for your sample volume.
- 100% browser-side
- Two-way conversion
- Instant recalculation
1Describe the protein
50,000 g/mol, so 1 nmol of this protein weighs 50 µg.
Common proteins
Not listed? Calculate the molecular weight from the sequence.
2Type the value you have into any box
The other boxes are calculated from it. Molecular weight links mass and moles; the sample volume links a concentration to a total.
Per mL
Concentration
In the tube
Needed only to connect a concentration with a total amount.
1 mg/mL of 50 kDa protein =
20 µM
What the math is doing
One division by the molecular weight, and one multiplication by the volume.
- 1µM = 1 mg/mL × 1,000 ÷ 50 kDa = 20 µM
- 2mg = 1 mg/mL × 1 mL = 1 mg
- 3nmol = 20 µM × 1 mL = 20 nmol
mg/mL is the same as g/L and a kDa is 1,000 g/mol, so µM = mg/mL × 1,000 ÷ kDa. Totals are the concentration times the sample volume: 1 µM in 1 mL is 1 nmol.
What 20 µM looks like up close
About 12 protein molecules in a cube of solution 100 nm on each side. That is 1.204 × 1016 molecules per mL.
At the same 1 mg/mL, this cube would hold about 104 insulin molecules (5.8 kDa), or about 4 IgG antibodies (150 kDa). The heavier each molecule, the fewer fit in the same mass, which is why molecular weight sets the molarity.
Each dot is one molecule, drawn to scale as a sphere of the protein’s volume.
Try a worked example
Load any scenario straight into the calculator above.
Why this calculator is useful
Protein concentration shows up in prep, QC, chromatography, assay design, and notebook-based analysis.
Two-way conversion
Convert from protein mass concentration to molarity, or enter a molar value and recover the equivalent mass concentration.
Sample-volume aware
Estimate total nmol and total mg in the sample volume you provide, which is useful for prep and downstream experiments.
Browser-side calculation
Everything runs locally in your browser. No upload, no login, and no dependency on a server-side calculator.
Unit reference
These are the conventions the calculator uses.
- mg/mL
- Numerically equal to g/L for aqueous protein solutions.
- µg/mL
- 1,000 µg/mL = 1 mg/mL.
- µM
- 1 µM in 1 mL equals 1 nmol.
- kDa
- 1 kDa = 1,000 g/mol, which makes the conversion straightforward.
Quick conversion rule
For protein concentration in mg/mL, use the molecular weight in kDa to move between mass and molar units.
µM = (mg/mL × 1000) / kDa
mg/mL = (µM × kDa) / 1000
1 µM in 1 mL = 1 nmol
Assumption: 1 Da is treated as 1 g/mol and the molecular weight you enter is used as-is. This is meant for quick concentration conversion, not extinction-coefficient-based quantification.
Frequently asked questions
A few quick answers before you use the calculator in a lab or notebook workflow.
It converts protein concentration between mass units and molarity using the molecular weight you enter. It also estimates total nmol in the sample volume.
Related tools
This calculator works best as one step inside a broader sequence and protein-analysis cluster.
- DNA Concentration CalculatorKeep DNA and protein prep calculations close together.
- GC Content CalculatorReturn to sequence-level QC before deeper analysis.
- Reverse ComplementPrep the upstream sequence if your protein work starts from DNA.
- A280 Protein Concentration CalculatorCalculate protein concentration from absorbance at 280 nm.
Runcell workflow handoffProtein analysis
Use this calculation before notebook-based protein analysis
Convert the numbers here, then move into Runcell for downstream interpretation, comparison, and notebook-based analysis.