Serial Dilution Calculator
Serial dilution repeatedly transfers a fixed volume into fresh diluent to produce a geometric series of concentrations. Enter your starting concentration, the transfer volume, the total volume per tube, and the number of steps to instantly find the final concentration and total dilution factor.
Concentration after all dilution steps
- 1
Dilution factor per step
df = 1 ÷ 10 = 0.1 - 2
Overall dilution factor (dfⁿ)
0.1ⁿ n = 3 = 0.001 - 3
Final concentration
C₀ × dfⁿ = 1 × 0.001 = 0.001000Same unit as the initial concentration entered.
How does this calculator work?
Each dilution step multiplies concentration by DF = Vt/Vf; after n steps the final concentration is C₀ × (Vt/Vf)ⁿ. Enter initial concentration, transfer volume, total tube volume and number of steps to get the final concentration and the total fold reduction.
Formula
How this is calculated
Each step of a serial dilution mixes a small transfer volume (Vₜ) with enough diluent to reach a fixed total volume (Vf). The resulting concentration is reduced by the dilution factor DF = Vₜ / Vf — for example, transferring 1 mL into a tube already containing 9 mL diluent (total 10 mL) gives DF = 0.1, a 1:10 dilution. Repeating this n times multiplies the factors: Cₙ = C₀ × DFⁿ.
The total dilution is the original concentration divided by the final concentration, often expressed as a fold reduction or a log₁₀ value (decades). A 1:10 dilution repeated 6 times gives a total factor of 10⁶ (1,000,000-fold), which is −6 on the log scale — the standard way microbiologists express colony-count plates.
This calculator assumes ideal mixing (no dead volume, no pipetting error) and that the diluent does not affect the analyte. Real-world serial dilutions accumulate pipetting errors at each step, so the last significant digit of your calculated concentration carries more uncertainty with each additional step.
Frequently asked questions
A serial dilution is a stepwise process of diluting a solution by a constant factor each time. A small volume is transferred from each tube into the next, so the concentration decreases geometrically (e.g. 1:10 per step means 10×, 100×, 1000× dilution after three steps).
Multiply the per-step dilution factors together. For identical steps, total DF = (Vt/Vf)ⁿ. The inverse (Vf/Vt)ⁿ is the fold reduction — how many times smaller the final concentration is compared to the starting concentration.
Any unit works — mg/mL, mol/L, CFU/mL, OD₆₀₀, etc. — as long as you are consistent. The calculator applies the dilution factor to whatever value you enter, so the result is in the same unit.
Also known as
TG we-Calculate Editorial Team. (2026). Serial Dilution Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/serial-dilution-calculator
TG we-Calculate Editorial Team. "Serial Dilution Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/serial-dilution-calculator.
TG we-Calculate Editorial Team, "Serial Dilution Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/serial-dilution-calculator
@misc{wecalculate_serial_dilution_calculator, title = {Serial Dilution Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/serial-dilution-calculator}}, year = {2026}, note = {TG we-Calculate} }
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