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

Pearson's square

A two-by-two arithmetic for blending two strengths to a target. Used in distilleries to bottle cask spirit, in cheesemaking for milk fat, and in juice production for brix.

§ 1Worked example · cask 60 % to bottle 46 %

  1. High = 60, low = 0 (water), target = 46.
  2. Parts of cask = target − low = 46 − 0 = 46.
  3. Parts of water = high − target = 60 − 46 = 14.
  4. Total parts = 60. Cask fraction = 46 ÷ 60 = 0.767.
  5. For a 700 ml bottle: cask = 536.7 ml; water = 163.3 ml.

Volumes are approximate above 30 % v/v. Ethanol-water mixtures contract on blending; HMRC spirit-strength tables convert v/v at 20 °C to the target abv after equilibration.[17]

§ 2Brix blending

  • Same arithmetic, brix in place of % ABV.
  • Used in juice and cordial production to hit a label strength.
  • Combine with a refractometer reading post-blend to verify.

§ 3Related