Serial Dilution Calculator
Use this serial dilution calculator to build a repeatable dilution plan, estimate transfer and diluent volumes, and preview the concentration in each tube of a dilution series.
Dilution Plan
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Formula
| Variable | Meaning | Unit |
|---|---|---|
| Vmin | Minimum volume needed in each tube | mL or uL |
| Vexp | Volume used per experiment or replicate | mL or uL |
| DF | Dilution factor per step | unitless |
| Vtransfer | Volume transferred from the previous tube | mL or uL |
| cn | Concentration in tube n | same as c1 |
- Choose the planning mode: Use dilution-factor mode when you already know the per-step dilution factor, or concentration-range mode when you know the stock concentration and the target first concentration.
- Set the number of dilutions: Pick how many tubes or steps you want in the series. The page then expands the concentration table automatically.
- Calculate transfer and diluent volumes: The calculator uses the chosen factor and minimum-volume rule to estimate the transfer from one tube to the next and the diluent required in each new tube.
- Review the concentration series: Check the table for the cumulative dilution factor and concentration at each step before preparing the actual samples.
Worked Examples
- Initial concentration: 100 mg/L
- Dilution factor: 10
- Steps: 6
- Experimental volume: 0.20 mL
- Repeats: 3
- Safety margin: 10%
Result: Minimum volume per tube is 0.66 mL and the sixth tube concentration is 0.001 mg/L.
A strong per-step dilution quickly drives the final concentration downward, so volume planning matters.
- Stock concentration: 10 mg/mL
- First tube concentration: 1 mg/mL
- Dilution factor: 5
- Tube volume: 2.0 mL
- Steps: 5
Result: The first tube needs 0.20 mL of stock and 1.80 mL of diluent.
The remaining tubes keep the same dilution factor, producing a predictable descending concentration series.
- Initial concentration: 1,000 CFU/mL
- Dilution factor: 2
- Steps: 4
- Experimental volume: 50 uL
- Repeats: 4
- Extra volume: 10 uL
Result: The calculator helps confirm whether your planned transfer volumes stay realistic for the pipette range.
Very small tube volumes can become error-prone even when the arithmetic is correct.
FAQ
References
This calculator helps with dilution planning, but your final protocol should still account for pipette limits, mixing efficiency, and any assay-specific handling losses.