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Sourdough hydration calculator
Three jobs on one screen: check your dough's true hydration with the starter counted, find the water for a target hydration, or build a recipe for any number of loaves. Grams or ounces.
How it works
A starter is part flour and part water. At 100% hydration it is half and half; at 50% hydration a third is water. The calculator splits your starter into its flour and water and adds them to the rest, so the hydration it shows is the true one.
Example: 500 g flour, 350 g water and 100 g of a 100% starter. The starter adds 50 g flour and 50 g water, so the dough has 550 g flour and 400 g water: 400 ÷ 550 = 72.7%, not the 70% you get if you leave the starter out.
To hit a target, the calculator works out the water needed for that hydration and takes away the water you already have. If you are already above the target, it tells you how much flour to add instead.
To build a recipe, it divides the total dough weight by 1 plus the hydration and salt as decimals to get the total flour, then takes the starter's flour and water out of the flour and water you add.
Questions people ask
Does starter count toward hydration?
Yes, if you want the true hydration. A starter is flour and water, so both are part of the dough. 100 g of starter at 100% hydration adds 50 g of flour and 50 g of water. A recipe of 500 g flour, 350 g water and 100 g starter is 70% if you leave the starter out, but (350 + 50) ÷ (500 + 50) = 72.7% when it is counted.
What is reverse baker's percentage?
Baker's percentages give every ingredient as a percentage of the flour weight, with the flour at 100%. Reverse baker's percentage starts from those percentages and a dough weight and works back to the grams to weigh. For 1,000 g of dough at 70% water and 2% salt, the flour is 1,000 ÷ 1.72 = 581 g.
Why grams instead of cups?
A cup measures volume, and how much flour fits in a cup changes with the flour and how you fill it. A weight doesn't depend on how you fill the cup, so recipes in grams give the same result every time. If you only have cups, weigh one cup of your flour once and type that in; the calculator then shows cups as a rough guide.
What does hydration mean?
Hydration is the weight of the water divided by the weight of the flour, as a percentage. 700 g of water with 1,000 g of flour is 70% hydration.
Does the calculator say how long to ferment?
No. It works out weights and ratios only. Fermentation depends on your starter, flour and kitchen, so follow your recipe for timings.