Dilution factor calculator explained
The dilution factor calculator shows how the ratio between total volume and stock aliquot controls concentration changes. Enter any pair of volumes: stock, diluent, or total, and the page solves for the missing values, so you can document serial dilutions or single-step mixes without re-deriving the math. It is handy when you need to prep calibration standards, microbiology plates, or QC samples that must hit an exact factor such as 1:5 or 1:100.
Use it before pipetting so you know how much diluent belongs in the tube, and keep it open while recording notebook entries to ensure the written factor matches what you prepared.
How the conversion works
For a single dilution, the fundamental relationships are:
Dilution factors multiply across serial steps, so the overall factor for identical steps is . The calculator mirrors these relationships by keeping {volume_initial}, {dilutant}, and {volume_final} synchronized in real time.
Units and conversions
| Quantity | Symbol | Common units | Notes |
|---|---|---|---|
| Stock volume | µL, mL | Keep consistent across all entries. | |
| Diluent volume | µL, mL | Can be expressed as a direct volume or as {stock_dilutant}. | |
| Total volume | µL, mL | Equals stock + diluent. | |
| Dilution factor | dimensionless | Often written as 1:x or $x×$ where . |
Multiplying or dividing by switches between µL and mL; the ratio itself remains unchanged.
Worked examples
- Single-step bleach prep
Goal: prepare 150 mL of a 1:5 dilution for surface disinfection. Set , solve for .
The calculator reports , so mix 30 mL stock with 120 mL water.
- Serial dilution for colony counts
Need an overall dilution starting with 1 mL stock. Use two 1:100 steps ( each). Each step uses and , so . After two steps: , giving the target thousand-fold decrease in concentration.
Tips and pitfalls
- Always record dilution factors as
1:xratios to avoid confusion between and its reciprocal. - When stacking steps, multiply the factors instead of summing volumes from earlier tubes.
- Match pipette accuracy to the smallest aliquot; large total volumes with tiny stock inputs magnify volumetric error.
- Document both and the actual volumes so audits can confirm how you achieved the factor.