What you are given
- Stock concentration: 1 M
- Fold factor: 10
- Number of tubes: 4
- Volume per tube: 1 mL
Formula: Cₙ = C₀ / fⁿ
Dilutions
How do you set up a serial dilution?
Each tube is the previous tube divided by the fold factor. Transfer volume is the volume per tube divided by the fold factor, and the rest of each tube is fresh diluent, pre-filled before you start.
Worked example
Every number below is computed by the calculator, not typed in
The working
- Per-tube concentration:
Cₙ = C_stock / fⁿ - Transfer volume:
V_t = V₂ / f = 1 mL / 10=0.1 mL - Diluent per tube:
V₂ − V_t=0.9 mL - Series:
4 step(s) of 10× from 1 M
4 tubes at a 10× dilution, from 1 M down to 0.0001 M.
What each symbol means
- Cₙ: Concentration in tube n (M)
- C₀: Stock concentration (M)
- f: Fold factor
- n: Tube number
A printable one-page version is on the formula sheet.
Where this usually goes wrong
- Not pre-filling the tubes with diluent. Pipetting into an empty tube and then adding diluent mixes unevenly.
- Forgetting to mix between steps. Every carried-over error multiplies down the whole series.
- Using the same tip throughout, which carries concentrated stock down the series.
Try it yourself
Two problems, with the working revealed
Problem 1 Serial dilution
Work out the concentration in each tube, the transfer volume, and the diluent per tube.
- Stock concentration: 500 µM
- Fold factor: 2
- Number of tubes: 6.5
- Volume per tube: 200 µL
Show the answer and the working
7 tubes at a 2× dilution, from 500 µM down to 3.906 µM.
- Per-tube concentration:
Cₙ = C_stock / fⁿ - Transfer volume:
V_t = V₂ / f = 200 µL / 2=100 µL - Diluent per tube:
V₂ − V_t=100 µL - Series:
7 step(s) of 2× from 500 µM
Open this in the calculator to change the numbers.
Problem 2 Serial dilution
Work out the concentration in each tube, the transfer volume, and the diluent per tube.
- Stock concentration: 1 M
- Fold factor: 10
- Number of tubes: 2
- Volume per tube: 1 mL
Show the answer and the working
2 tubes at a 10× dilution, from 1 M down to 0.01 M.
- Per-tube concentration:
Cₙ = C_stock / fⁿ - Transfer volume:
V_t = V₂ / f = 1 mL / 10=0.1 mL - Diluent per tube:
V₂ − V_t=0.9 mL - Series:
2 step(s) of 10× from 1 M
Open this in the calculator to change the numbers.
Do it with your own numbers.
The Serial dilution calculator is free, shows every step, flags the hazards, and works offline once loaded. No account, no signup.
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