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

Dilution error sources

Routine work tolerates ±2 % per step. Quantitative work tolerates ±0.5 %. Knowing where the error budget goes lets you spend it deliberately.

§ 1Per-pipette error

  • P1000 at nominal (1 000 µl): accuracy ±0.6 %, precision ±0.2 %.
  • P200 at nominal (200 µl): accuracy ±0.8 %, precision ±0.25 %.
  • P20 at 2 µl (10 % of nominal): accuracy ±5 %, precision ±2 %.
  • Class A volumetric flask, 250 ml: ±0.04 % at calibration temperature (20 °C).

§ 2Propagation across a serial

Random errors add in quadrature. Six 1:10 steps each at ±1 % give a combined uncertainty of √6 × 1 % ≈ 2.4 % on the final concentration. Systematic errors (un-calibrated pipette, wrong stock) add linearly and dominate beyond two steps.[23]

§ 3Other sources

  • Meniscus parallax. Eye level with the meniscus, bottom of the curve on the line.
  • Temperature. Glassware is calibrated at 20 °C; cold room work biases volumes ~0.05 % per °C cooler.
  • Wetting and bubble retention. Tips not pre-wetted give a low first aspirate.
  • Adsorption. Detergents adsorb to plastic; pre-rinse a polypropylene tip for surfactant work.

§ 4Related