How It Works
This calculator works in 4 steps.
Enter sample concentrations
Type each sample's concentration, such as µg/µL protein.
Enter the target mass
Type the mass per lane or reaction, such as 20 µg.
Enter the loading volume
Type the volume each lane receives before loading dye.
Read the volumes
The calculator returns sample and buffer volumes and flags samples exceeding the loading volume.
The Formula
The formula divides the target mass by each sample's concentration.
Vᵢ = m / CᵢV_buf,i = V_load − VᵢVᵢ ≤ V_load- m:
- Target mass per sample
- Cᵢ:
- Concentration of sample i
- V_load:
- Equal loading volume
To load 20 µg from a 2.8 µg/µL lysate in 15 µL, add 7.14 µL lysate and 7.86 µL lysis buffer.
Conversion Table
The conversion table gives sample and buffer volumes for 20 µg per lane in 15 µL for 6 lysates.
| Lane | Concentration | Sample volume | Buffer | Mass loaded |
|---|---|---|---|---|
| Lane 1 | 4.2 µg/µL | 4.762 µL | 10.24 µL | 20 µg |
| Lane 2 | 2.8 µg/µL | 7.143 µL | 7.857 µL | 20 µg |
| Lane 3 | 3.5 µg/µL | 5.714 µL | 9.286 µL | 20 µg |
| Lane 4 | 1.9 µg/µL | 10.53 µL | 4.474 µL | 20 µg |
| Lane 5 | 5.6 µg/µL | 3.571 µL | 11.43 µL | 20 µg |
| Lane 6 | 2 µg/µL | 10 µL | 5 µL | 20 µg |
What Is the Equal-Mass Sample Calculator?
The Equal-Mass Sample Calculator is a tool that returns the volume of each sample needed to deliver the same mass, such as 20 µg protein per gel lane, and the buffer volume that brings every sample to an equal loading volume. The tool divides the target mass by each sample's concentration.
Equal-mass loading is the basis of fair comparison in western blots, SDS-PAGE, and enzyme activity panels. The calculator checks that the largest sample volume fits within the well or tube limit and flags samples too dilute to deliver the target mass.
Common Uses
There are 5 main uses of this calculator.
Western blots
Users load 10 to 50 µg protein per lane.
SDS-PAGE
Labs compare protein patterns at equal mass.
Enzyme activity panels
Biochemists add equal protein mass to each assay.
Proteomics
Mass spectrometry labs digest equal protein mass per sample.
Immunoprecipitation
Users start IP with equal lysate mass.