Serial Dilution Concentration Calculator
Find the concentration at every stage of a serial dilution from the stock concentration, the fold-dilution per step and the number of steps.
How it works
Cₙ = C₀ / Dⁿ · total dilution factor = Dⁿ (D = fold per step, n = number of steps)
A serial dilution repeats the same fold-dilution over several stages, so each step multiplies the total dilution rather than adding to it. That geometric compounding lets a single stock reach extremely low, evenly spaced concentrations — the backbone of standard curves, plate assays and microbiology counts. The concentration after n identical steps is simply the starting concentration divided by the dilution factor raised to the power n.
Worked example
Start with 1 M stock and dilute 10-fold at each of 5 steps: the total dilution factor is 10⁵ = 100,000, so the final concentration is 1 / 100,000 = 1 × 10⁻⁵ M. The intermediate tubes read 0.1, 0.01, 0.001 and 0.0001 M.
Sources: Serial dilution — Wikipedia
Frequently asked questions
What does "10-fold dilution" mean in practice?
Take one part of the solution and add nine parts of diluent for a total of ten parts. Each such transfer divides the concentration by ten, and repeating it builds the series.
Why use a serial dilution instead of one big dilution?
Diluting by a huge factor in one step requires impractically tiny volumes and large errors. Splitting it into several modest steps keeps every pipetting volume accurate and gives you the intermediate concentrations for free.
Do all steps have to use the same fold?
This calculator assumes a constant fold per step, which is the usual laboratory practice. If steps differ, multiply the individual dilution factors together to get the total.
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This calculator is for educational purposes. Double-check important results before acting on them.