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Dough hydration calculator

A starter is roughly half water, and that water counts toward hydration. Ignoring it is the commonest reason a dough comes out wetter than intended.

Flour

Target hydration

%

Starter

Starter hydration

%

Water to add

725.0g

= Exact Dough hydration Show in

Water already in the starter: 100.0
Flour already in the starter: 100.0
Total flour in the dough: 1100.0
Total dough weight: 1925
How far out the naive answer would be: 25.0

Show the working

Flour = 1000
Target hydration = 75
Starter = 200
Starter hydration = 100
Water already in the starter = 200 * (100/100) / (1 + 100/100) = 100
Flour already in the starter = 200 - 100 = 100
Total flour in the dough = 1000 + 100 = 1100
total_water_needed = 1100 * 75/100 = 825
Water to add = 825 - 100 = 725
Total dough weight = 1100 + 825 = 1925
naive = 1000 * 75/100 = 750
How far out the naive answer would be = 750 - 725 = 25

Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.

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The formula

a starter at h% hydration is h/(100+h) water by weight
total flour = recipe flour + starter flour
water to add = total flour x target hydration - starter water

A 100% hydration starter is exactly half flour and half water by weight.

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