How It Works
This calculator works in 4 steps.
Enter the starting concentration (C₀)
Type the stock concentration in any unit, such as 1 mg/mL or 10⁸ cells/mL.
Set the factor per step
Choose a factor, such as 2, 3, 5, or 10.
Set tube count and working volume
Type the number of tubes and the volume each tube holds after transfer.
Read the tube table
The calculator lists Cₙ, cumulative DF, transfer volume, and diluent volume for every tube.
The Formula
The formula divides the starting concentration by the step factor raised to the tube number.
Cₙ = C₀ / FⁿDFₙ = FⁿV_t = V_working / (F − 1)V_d = V_working- Cₙ:
- Concentration in tube n
- C₀:
- Starting concentration
- F:
- Factor per step
- n:
- Tube number
- V_working:
- Volume left in each tube after its transfer out
A 1,000 µg/mL stock in a 5-fold series gives 200, 40, 8, 1.6, and 0.32 µg/mL in tubes 1 to 5. For 400 µL kept per tube, transfer 100 µL into 400 µL of diluent at each step.
Conversion Table
The conversion table shows a 7-tube, 5-fold series from 1,000 µg/mL with concentrations in µg/mL and ng/mL.
| Tube | Cumulative DF | Concentration (µg/mL) | Concentration (ng/mL) |
|---|---|---|---|
| Tube 1 | 5 | 200 µg/mL | 200,000 ng/mL |
| Tube 2 | 25 | 40 µg/mL | 40,000 ng/mL |
| Tube 3 | 125 | 8 µg/mL | 8,000 ng/mL |
| Tube 4 | 625 | 1.6 µg/mL | 1,600 ng/mL |
| Tube 5 | 3,125 | 0.32 µg/mL | 320 ng/mL |
| Tube 6 | 15,625 | 0.064 µg/mL | 64 ng/mL |
| Tube 7 | 78,125 | 0.0128 µg/mL | 12.8 ng/mL |
What Is the Serial Dilution Calculator?
The Serial Dilution Calculator is a multi-step tool that returns the concentration, cumulative dilution factor, transfer volume, and diluent volume for each tube in a chain of sequential dilutions. Each tube is made from the previous tube, so the dilution factor compounds at every step.
Serial dilution reaches very low concentrations with practical pipette volumes. A 10⁻⁶ dilution in one step needs 1 µL in 1 L (0.26 US gal); a 6-step tenfold series needs 100 µL into 900 µL six times. The calculator supports any starting concentration, any step factor, and up to 24 tubes.
Common Uses
There are 6 main uses of this calculator.
Standard curves
Analysts prepare ELISA and qPCR standards across 3 to 7 orders of magnitude.
Bacterial plate counts
Microbiologists dilute cultures until plates hold 30 to 300 colonies.
Minimum inhibitory concentration (MIC) tests
Labs build twofold antibiotic series in broth.
Antibody and virus titrations
Researchers find the end-point dilution of a reagent or virus stock.
Dose-response series
Pharmacologists prepare 8 to 12 concentrations for IC₅₀ curves.
Limiting dilution cloning
Cell biologists dilute cells to about 1 cell per well.