Serial Dilution Calculator
A serial dilution applies the same dilution factor repeatedly, with each diluted solution feeding the next step. This produces a geometric series of concentrations and lets you reach very large total dilutions using practical pipetting volumes. The final concentration equals the starting concentration divided by the per-step factor raised to the number of steps. This calculator reports the final concentration and the total dilution factor from your starting concentration, the per-step factor, and the number of steps. It is widely used for standard curves, microbial counts, and immunoassays.
Serial dilution formula
total dilution factor = (per-step factor) ^ (number of steps)
final concentration = starting concentration / total dilution factor
each step: new concentration = previous / per-step factor
The starting concentration must be zero or greater, the per-step factor must be greater than 1, and the number of steps must be zero or greater. The final concentration is in the same units as the start.
Serial dilution context
- Each step divides the concentration by the same per-step factor.
- The total dilution factor is the per-step factor raised to the number of steps.
- A 1-in-10 dilution repeated 3 times gives a total factor of 1,000.
- Serial dilution reaches large dilutions with accurate, practical pipetting volumes.
- It underpins standard curves, plate counts, and antibody titration.
Serial dilution: frequently asked questions
What is a serial dilution?
A serial dilution is a stepwise dilution where the product of each step becomes the starting solution for the next. Each step reduces the concentration by the same dilution factor, producing a geometric series of concentrations useful for assays and standard curves.
How do I calculate a serial dilution?
Divide the starting concentration by the dilution factor raised to the number of steps: final = initial / (factor ^ steps). For a 1-in-10 dilution repeated 3 times, the total factor is 10^3 = 1,000, so the final concentration is one thousandth of the start.
What is the dilution factor?
The dilution factor is the ratio of final volume to the volume of the more concentrated solution transferred at each step. A 1-in-10 dilution has a factor of 10, meaning 1 part stock is diluted to a total of 10 parts. Enter the per-step factor here.
What is the total dilution factor?
The total dilution factor is the per-step factor raised to the number of steps. It tells you how many times more dilute the final solution is compared to the starting solution. For four 1-in-5 steps it is 5^4 = 625.
Why use serial dilution instead of a single dilution?
Serial dilution achieves very large dilution factors accurately using manageable volumes, avoiding the tiny, error-prone transfers a single huge dilution would need. It is standard in microbiology, immunoassays, and any work requiring a range of concentrations.
Official sources
- NIST: measurement and concentration reference resources.
- BIPM: SI units for amount-of-substance concentration.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.