Sourdough Calculator

Baker's percentages express every ingredient against the flour, which is always 100%. Water at 75% means 750 g of water for every 1,000 g of flour. It looks odd at first — the percentages add up to well over 100 — but it makes a recipe scale to any batch size without breaking, which cup measurements never do.

The part almost every calculator gets wrong is the starter. A starter at 100% hydration is half flour and half water, so a recipe using 200 g of starter is quietly adding 100 g more flour and 100 g more water than the headline numbers suggest.

That is why this calculator shows two hydration figures. Recipe hydration is the number you typed. True hydration counts the starter's contribution, and it is the one that describes how the dough will actually feel in your hands.

1. Step 1 Everything is a percentage of flour water = flour × hydration% starter = flour × starter% salt = flour × salt%
2. Step 2 Total dough weight dough = flour + water + starter + salt
3. Step 3 Working backwards from a target flour = target_dough ÷ (1 + hydration% + salt% + starter%) This is how you scale to fit your tins or bannetons.
4. Step 4 True hydration total_flour = flour + starter ÷ 2 total_water = water + starter ÷ 2 true_hydration = total_water ÷ total_flour Assumes a 100% hydration starter — equal flour and water.
5. Step 5 Split across loaves per_loaf = total_dough ÷ number_of_loaves

Example: 500 g flour at 75% hydration, 2% salt and 20% starter gives 375 g water, 10 g salt and 100 g starter — 985 g of dough. True hydration is 425 ÷ 550 = 77.3%, slightly wetter than the 75% on the label.

• The starter is assumed to be at 100% hydration — equal weights of flour and water — which is the most common maintenance ratio. A stiff starter at 50% or a liquid levain at 125% changes the true hydration figure significantly.
• True hydration includes the starter's flour and water. Some recipes and calculators quote hydration excluding the starter, so the same dough can be described as 75% or 77% depending on convention. Both are shown here.
• Salt is calculated on added flour rather than total flour including the starter. The difference is small — under 0.2% on a typical recipe — but it is the more common convention.
• No allowance is made for evaporation during baking. A finished loaf weighs roughly 10 to 15 percent less than the dough that went in.
• Fermentation timing is not modelled at all, because it depends on dough temperature, starter activity and ambient conditions far more than on the ratios. A dough at 78 °F ferments about twice as fast as the same dough at 68 °F.
• Add-ins such as seeds, nuts, oil, honey and inclusions are not included. Seeds in particular absorb water and will effectively lower your hydration unless soaked first.
• Whole grain and rye flours absorb considerably more water than white bread flour. A 75% hydration dough made with 30% whole wheat behaves more like a 70% white dough.