How It Works
This calculator works in 4 steps.
Enter the stock concentration
Type the measured value in mg/mL, or in µM with the protein MW.
Enter the target concentration
Type the working value; the calculator converts between mass and molar units with MW in kDa.
Enter the final volume
Type the volume in µL or mL.
Read the volumes
The calculator returns protein stock and buffer volumes and flags targets below 0.1 mg/mL.
The Formula
The formula applies C₁V₁ = C₂V₂ and links mass and molar units through molecular weight.
V₁ = C₂ × V₂ / C₁µM = (mg/mL) × 10⁶ / MW (g/mol)MW (g/mol) = kDa × 1,000- C₁ / C₂:
- Stock and target protein concentration
- V₁ / V₂:
- Stock and final volumes
- MW:
- Protein molecular weight
To make 200 µL of 0.5 mg/mL from a 5.2 mg/mL stock, V₁ = 0.5 × 200 / 5.2 = 19.2 µL protein and 180.8 µL buffer. For a 50 kDa protein, 0.5 mg/mL equals 10 µM.
Conversion Table
The conversion table gives protein and buffer volumes for 6 protein dilutions.
| Stock | Target | Final volume | Protein stock | Buffer |
|---|---|---|---|---|
| 10 mg/mL | 1 mg/mL (1,000 µg/mL) | 1,000 µL | 100 µL | 900 µL |
| 5.2 mg/mL | 0.5 mg/mL (500 µg/mL) | 200 µL | 19.23 µL | 180.8 µL |
| 2 mg/mL | 0.1 mg/mL (100 µg/mL) | 500 µL | 25 µL | 475 µL |
| 25 mg/mL | 2 mg/mL (2,000 µg/mL) | 100 µL | 8 µL | 92 µL |
| 1.5 mg/mL | 0.025 mg/mL (25 µg/mL) | 1,000 µL | 16.67 µL | 983.3 µL |
| 40 mg/mL | 4 mg/mL (4,000 µg/mL) | 50 µL | 5 µL | 45 µL |
What Is the Protein Dilution Calculator?
The Protein Dilution Calculator is a tool that returns the protein stock volume and buffer volume needed to reach a working protein concentration in mg/mL, µg/mL, or µM. The calculator converts mass and molar units using the protein's molecular weight in kilodaltons (kDa).
Protein concentration comes from an absorbance reading at 280 nm (A280), a BCA assay, or a Bradford assay. Dilution follows C₁V₁ = C₂V₂, and the choice of diluent matters: proteins below about 0.1 mg/mL stick to plastic tubes, so many protocols add a carrier such as 0.1% BSA. The calculator notes this low-concentration range.
Common Uses
There are 5 main uses of this calculator.
Assay inputs
Researchers dilute purified protein for activity and binding assays.
Crystallography screens
Structural biologists set protein to 5 to 20 mg/mL for drops.
Binding studies
Biophysicists dilute protein to µM levels for ITC and SPR.
SDS-PAGE loading
Users dilute samples before mixing with loading dye.
Enzyme kinetics
Biochemists set enzyme concentration in nM for reaction setups.