How It Works
This calculator works in 3 steps.
Enter the stock volume
Type the concentrate volume, such as 10 mL.
Enter the diluent volume
Type the volume of water or buffer added, such as 90 mL.
Read the 1:X ratio
The calculator divides diluent volume by stock volume to give X.
Read the matching DF
The calculator adds 1 to X to give the dilution factor and the total volume.
The Formula
The formula divides the diluent volume by the stock volume.
X = V_diluent / V_stock1 : XDF = X + 1- V_stock:
- Concentrate volume
- V_diluent:
- Diluent volume added
- X:
- Diluent parts per 1 part stock
- DF:
- Dilution factor
Mixing 25 mL of concentrate with 75 mL of water gives X = 75 / 25 = 3, a 1:3 stock-to-diluent ratio and a DF of 4.
Conversion Table
The conversion table turns 7 measured volume pairs into a 1:X ratio, total volume, and DF.
| Stock | Diluent | Stock:diluent | Total volume | Matching DF |
|---|---|---|---|---|
| 10 mL | 90 mL | 1:9 | 100 mL | 10 |
| 25 mL | 75 mL | 1:3 | 100 mL | 4 |
| 5 mL | 495 mL | 1:99 | 500 mL | 100 |
| 1 mL | 1 mL | 1:1 | 2 mL | 2 |
| 50 mL | 200 mL | 1:4 | 250 mL | 5 |
| 2 mL | 18 mL | 1:9 | 20 mL | 10 |
| 0.5 mL | 99.5 mL | 1:199 | 100 mL | 200 |
What Is the Stock-to-Diluent Ratio Calculator?
The Stock-to-Diluent Ratio Calculator is a tool that expresses a dilution as the volume of concentrate relative to the volume of diluent added, written as 1:X. A 1:9 stock-to-diluent ratio means 1 mL of stock plus 9 mL of diluent, which equals a dilution factor of 10.
The stock-to-diluent form is common in microbiology, cleaning, and photographic chemistry. The calculator converts measured volumes into the 1:X ratio and shows the matching dilution factor (DF = X + 1), so the ratio does not get confused with the stock-to-final convention.
Common Uses
There are 5 main uses of this calculator.
Recipe recording
Users record a home-made mix as a ratio for repeat batches.
Microbiology blanks
Microbiologists describe 1 mL into 9 mL blanks as a 1:9 stock-to-diluent step.
Ratio checks
Supervisors confirm that a staff-prepared mix matches the 1:X label ratio.
Label matching
Users match measured volumes to a label written in the parts-to-parts form.
Convention teaching
Instructors show the difference between 1:9 stock-to-diluent and 1:10 stock-to-total.