dilutioncalculator.co.uk§ Verified 20 Jun 2026 · Reviewed by A. Hargreaves, MChem (Hons)

Serial dilution calculator

Default 10-fold serial: transfer 1 ml into 9 ml of diluent at each step. Used in microbiology plate counts and lab assays where the final concentration is very small.

§ MeasureDesk
Concentrate
76.9 ml
Water
4 923.1 ml
Total at strength
5 000 ml
1.54 % v/v
§ PourScale · true-to-ratio
concentrate 1.54 %water 98.46 %

§ 1Why serial

A single 1:1 000 000 dilution is hard to make accurately because a 1 µl error in the stock dominates. Six 1:10 steps reach the same target while keeping each transfer in a forgiving 1 ml range.[10]

§ 2Common errors

  • Carry-over from un-rinsed tips. Use a fresh tip at each step.
  • Pipette accuracy drops below 10 % of the nominal volume. A 10 µl pipette on 0.5 µl is worse than a 1 ml pipette on 100 µl.
  • Mixing inadequate. Vortex 5 seconds between steps; pipette-mix five times if no vortex.
  • Temperature change. Water expands ~0.02 % per °C; for 4-figure work, equilibrate diluent.

§ 3Related