Sourdough Hydration Calculator
Calculate flour, water, starter and salt for any sourdough hydration using baker's percentages, with the starter's own flour and water accounted for.
- Flour to weigh
- —
- Water to weigh
- —
- Starter (levain)
- —
- Salt
- —
- Total dough weight
- —
- Overall hydration
- —
Percentages are baker's percentages against the total flour — the flour you weigh out plus the flour already living in your starter.
| Ingredient | Weight | Baker's % |
|---|---|---|
| Total flour | — | 100% |
| Total water | — | — |
| Salt | — | — |
| Starter | — | — |
- Overall hydration
- —
- Total flour
- —
- Total water
- —
- Salt (baker's %)
- —
- Starter (baker's %)
- —
- Total dough weight
- —
Rough guide: 65–70% is an easy, shapeable dough; 75–80% gives an open crumb but needs confident handling; above 85% you are into slack, ciabatta-style territory. Whole grain and rye flours drink more water than white bread flour, so nudge the number up when you use them.
How it works
This calculator uses standard baker's percentages on the overall formula:
every ingredient is expressed as a percentage of the total flour weight, and total
flour is always 100%. Hydration is therefore
total water ÷ total flour × 100. Crucially, your starter is part of that total —
a 100% hydration starter is half flour and half water by weight, so 100 g of it contributes
50 g of flour and 50 g of water. The calculator splits the starter for you
(starter flour = starter ÷ (1 + starter hydration ÷ 100)) and subtracts both
halves from what you still need to weigh out, which is why "flour to weigh" and "water to
weigh" are lower than the totals in the table.
Worked example: 500 g total flour at 75% hydration with 20% starter (100% hydration) and 2% salt gives 100 g starter (50 g flour + 50 g water), 375 g total water and 10 g salt — so you weigh out 450 g flour and 325 g water, for 885 g of dough. Switch to "total dough weight" if you want to hit a fixed loaf size instead, or use the second mode to reverse-engineer the hydration of a recipe you already bake. Everything is plain arithmetic running in your browser: no uploads, no accounts, no ads, and the numbers never leave your device.
Frequently asked questions
How is sourdough hydration calculated?
Hydration is total water divided by total flour, times 100. It is a baker's percentage, so total flour is always 100%: 375 g of water with 500 g of flour is 75% hydration. Both totals must include the flour and water hiding inside your starter, which is what this calculator does for you.
Does my starter count towards the hydration?
Yes. A 100% hydration starter is half flour and half water by weight, so 100 g of it adds 50 g of flour and 50 g of water to the formula. Ignore that and your dough bakes at a different hydration than you intended. The calculator splits the starter using starter flour = starter ÷ (1 + starter hydration ÷ 100) and subtracts both halves from the flour and water you still need to weigh out.
What hydration should I use for sourdough bread?
65–70% gives a firm, easy-to-shape dough that suits beginners and sandwich loaves. 75–80% is the classic open-crumb country loaf and needs confident stretch-and-folds. Above 85% the dough is slack and ciabatta-like. Whole grain, spelt and rye absorb more water, so add roughly 5–10 percentage points when they make up a large share of the flour.