How to use this calculator
- Enter the starting concentration.
- Enter the transfer and diluent volumes in the same unit.
- Enter the number of repeated equal dilution steps.
- Calculate and confirm the final concentration is within the measurement range.
#3300 · Science & Engineering Tool
Serial Dilution Dilution Factor Calculator
Calculate the cumulative dilution factor and final concentration after repeated equal serial-dilution steps. Enter starting concentration, transfer volume, diluent volume, and number of steps. The calculator reports the per-step factor, overall factor, final concentration, and the fraction of the original concentration remaining.
Calculator
Cumulative dilutionFormula
Per-step factor = (transfer + diluent) ÷ transfer
Overall factor = per-step factorsteps
Final concentration = starting concentration ÷ overall factor
Overall factor = per-step factorsteps
Final concentration = starting concentration ÷ overall factor
What the result means
The main result is the cumulative fold dilution from the original sample to the final serial-dilution level.
The formula assumes complete mixing, identical transfer and diluent volumes at every step, and no analyte loss beyond intentional dilution.
Example calculation
Transferring 100 µL into 900 µL gives a 10-fold step. Repeating six steps gives an overall factor of 1,000,000×. A 1000 µg/mL start becomes 0.001 µg/mL.
Tips for better results
- Use the same unit for transfer and diluent volumes.
- Mix completely before every transfer.
- Avoid transfer volumes near the lower accuracy limit of the pipette.
- Track step labels carefully because one skipped tube changes the result by a full factor.
- Use fewer steps or a smaller factor when the final concentration would fall below detection.
Frequently asked questions
Is a 1 to 10 dilution made with one part sample and ten parts diluent?
Often the intended 10-fold dilution is one part sample in ten parts total, meaning one part sample plus nine parts diluent.
How are serial dilution factors combined?
Multiply the factor from each step; equal steps are calculated by raising the per-step factor to the number of steps.
Can the number of steps be zero?
Yes. Zero steps gives an overall factor of 1 and leaves the starting concentration unchanged.
What if transfer and diluent volumes use different units?
Convert them to the same unit first; only their ratio is used.
Does removing liquid after mixing change the concentration?
No, a well-mixed aliquot has the same concentration as its source, although the amount remaining in the tube decreases.
Related calculators
Variables and units
| Variable | Meaning | Unit |
|---|---|---|
| Vt | Volume transferred each step | µL |
| Vd | Diluent in each receiver | µL |
| DFstep | (Vt + Vd) ÷ Vt | fold |
| DFoverall | DFstep raised to step count | fold |