How It Works
This converter works in 3 steps.
Enter the ratio
Type the ratio as 1:X, such as 1:9.
Select the source convention
Choose stock-to-diluent (parts to parts) or stock-to-final (parts of total).
Read the converted ratio
The calculator adds or subtracts 1 from X to switch conventions.
Read the DF and volumes
The result lists DF and the stock and diluent volumes for 10 mL of mix.
The Formula
The formula adds 1 to the diluent term to reach the final term, and subtracts 1 to reverse the conversion.
1 : X → 1 : (X + 1)1 : Y → 1 : (Y − 1)DF = X + 1 = Y- X:
- Diluent parts in the stock-to-diluent form
- Y:
- Total parts in the stock-to-final form
- DF:
- Dilution factor
A label reads 1:9 (1 part concentrate, 9 parts water). The stock-to-final form is 1:10, and DF = 10. For 100 mL total, use 10 mL concentrate and 90 mL water.
Conversion Table
The conversion table maps 8 ratios between the stock-to-diluent and stock-to-final conventions.
| Stock:diluent | = Stock:final | DF | Stock:final | = Stock:diluent |
|---|---|---|---|---|
| 1:1 | 1:2 | 2 | 1:1 | — (undiluted) |
| 1:2 | 1:3 | 3 | 1:2 | 1:1 |
| 1:3 | 1:4 | 4 | 1:3 | 1:2 |
| 1:4 | 1:5 | 5 | 1:4 | 1:3 |
| 1:9 | 1:10 | 10 | 1:9 | 1:8 |
| 1:10 | 1:11 | 11 | 1:10 | 1:9 |
| 1:19 | 1:20 | 20 | 1:19 | 1:18 |
| 1:99 | 1:100 | 100 | 1:99 | 1:98 |
What Is the Dilution Ratio Convention Converter?
The Dilution Ratio Convention Converter is a tool that translates a ratio written in one convention, stock-to-diluent or stock-to-final, into the other convention and into a dilution factor. A 1:4 stock-to-diluent ratio equals a 1:5 stock-to-final ratio, and both equal a DF of 5.
The two conventions differ by 1 part. A misread convention changes the final concentration by 10% at 1:9 and by 50% at 1:1. The converter shows both forms side by side and labels each one, so a protocol reader sees the exact volumes behind the ratio.
Common Uses
There are 5 main uses of this converter.
Label reading
Users check whether a 1:10 cleaning label means 10 or 11 total parts.
Protocol harmonization
Lab managers rewrite all ratios in an SOP set into one convention.
Error investigation
QC staff test whether a 10% concentration error came from a convention mix-up.
SOP writing
Authors state both forms in an SOP for clarity.
Staff training
Trainers show new staff how 1:1 means a 2-fold dilution in the parts-to-parts form.