How It Works
This calculator works in 3 steps.
Enter the stock volume
Type the volume of concentrate used.
Enter the final volume
Type the total volume after mixing.
Read the 1:X ratio
The calculator divides the final volume by the stock volume. X equals the dilution factor.
Read the diluent volume
The calculator subtracts the stock volume from the final volume.
The Formula
The formula divides the final volume by the stock volume.
X = V_final / V_stock1 : X (X = DF)% stock = 100 × V_stock / V_final- V_stock:
- Concentrate volume
- V_final:
- Total final volume
- X:
- Final parts per 1 part stock
- DF:
- Dilution factor
Adding 5 mL of stock to a 20 mL total gives X = 20 / 5 = 4, a 1:4 stock-to-final ratio. The diluent volume is 15 mL, and the stock forms 25% of the mix.
Conversion Table
The conversion table converts 7 stock and final volume pairs into a 1:X ratio, diluent volume, and stock percent.
| Stock | Final volume | Stock:final | Diluent | Stock share |
|---|---|---|---|---|
| 10 mL | 100 mL | 1:10 | 90 mL | 10% |
| 1 mL | 1,000 mL | 1:1,000 | 999 mL | 0.1% |
| 5 mL | 20 mL | 1:4 | 15 mL | 25% |
| 2 mL | 50 mL | 1:25 | 48 mL | 4% |
| 25 mL | 100 mL | 1:4 | 75 mL | 25% |
| 0.1 mL | 10 mL | 1:100 | 9.9 mL | 1% |
| 50 mL | 250 mL | 1:5 | 200 mL | 20% |
What Is the Stock-to-Final Ratio Calculator?
The Stock-to-Final Ratio Calculator is a tool that expresses a dilution as the volume of concentrate relative to the total volume of the finished solution, written as 1:X. A 1:10 stock-to-final ratio means 1 mL of stock in 10 mL total, which equals a dilution factor of 10.
The stock-to-final form is standard in biochemistry, immunology, and clinical chemistry. Antibody dilutions such as 1:1000 follow this convention. The calculator returns the 1:X ratio, the diluent volume, and the stock fraction as a percent of the total.
Common Uses
There are 5 main uses of this calculator.
Antibody working dilutions
Researchers describe 10 µL antibody in 10 mL buffer as 1:1000.
Serum and plasma dilutions
Clinical labs report sample dilutions such as 1:2 and 1:5 in stock-to-final form.
Clinical report correction
Lab systems multiply results by the X value to correct diluted samples.
Methods writing
Authors state ratios in the stock-to-final convention for journal methods sections.
Protocol transfer
Labs confirm that a partner lab's 1:X ratio matches the stock-to-final convention.