Gravity Blending & Dilution Calculator (Pearson Square)

How it works

Pearson square: parts of A = target − B; parts of B = A − target; volume of B = volume of A × (A − target) ÷ (target − B)

The Pearson square is the winemaker’s and brewer’s tool for blending to a number — mix two components of known strength and read off the proportions that give the target. It works because gravity points and alcohol percentages both blend (almost) linearly with volume. Diluting is just blending with water, which has zero points or zero alcohol: a high-gravity wort brewed to save kettle space is stretched to batch strength, a spirit is cut to bottling proof, a too-strong wine is tempered with a lighter one. The same square gives blending ratios for acidity, sugar or colour. It assumes no volume change on mixing, which is accurate for worts and wines and within a percent or two for spirits and water.

Worked example

18 L of 1.072 wort diluted to 1.056 with water: parts A = 56, parts B = 16 → add 18 × 16/56 = 5.1 L of water for 23.1 L at 1.056.

Frequently asked questions