Browse calculators

✨ Everyday

Sourdough calculator

Enter your flour weight and target percentages. The starter is split into its flour and water for you.

Free · no signup Runs in your browser

Total dough—

    Including what the starter contributes

      How do you calculate sourdough hydration?

      Divide the total water by the total flour, counting what is inside your starter. A 100% hydration starter is half flour and half water by weight, so 100 g of starter contributes 50 g of each. Ignoring that makes a dough look wetter than it is.

      Why published recipes disagree about hydration

      Two bakers can describe the same dough as 70% and 75% hydration, and both can be telling the truth as they calculate it. The difference is whether the starter is counted.

      A recipe with 500 g flour, 350 g water and 100 g of 100% hydration starter contains 550 g of flour and 400 g of water in total. That is 72.7% true hydration, but 70% if you only count the flour and water you added directly.

      Neither convention is wrong, but mixing them is. The calculator shows both figures so you can match whichever your recipe source uses.

      Baker's percentages

      Everything is expressed against total flour at 100%.

      • starter splits into flour and water:
      • starter flour = starter ÷ (1 + starter hydration)
      • starter water = starter − starter flour
      • total flour = added flour + starter flour
      • total water = total flour × hydration
      • water to add = total water − starter water
      • salt = total flour × salt %

      A 100% hydration starter contains equal weights of flour and water, so it divides in half. A 50% hydration stiff starter is two parts flour to one part water, so 150 g of it contributes 100 g flour and 50 g water.

      Salt is almost always 2% of total flour. Below about 1.5% the dough ferments too fast and tastes flat; above about 2.5% fermentation slows noticeably and the crumb tightens.

      Worked example: a 75% hydration loaf

      500 g of flour, 75% target hydration, 20% starter at 100% hydration, and 2% salt.

      1. Starter = 500 × 20%100 g
      2. Starter splits into50 g flour, 50 g water
      3. Total flour = 500 + 50550 g
      4. Total water = 550 × 75%412.5 g
      5. Water to add = 412.5 − 50362.5 g
      6. Salt = 550 × 2%11 g

      500 g flour, 362.5 g water, 100 g starter and 11 g salt, for 973.5 g of dough.

      Ignoring the starter would have you add the full 375 g of water for a nominal 75%, giving a true hydration of 77.3% — noticeably slacker, and a common reason a familiar recipe suddenly feels unmanageable.

      Choosing a hydration

      • Below 65% — stiff, easy to shape, tight crumb, good for sandwich loaves
      • 65% to 75% — forgiving and a sensible place to start
      • 75% to 85% — slack and sticky, capable of an open crumb with careful handling
      • Above 85% — batter-like, needs coil folds and a confident hand
      • Wholemeal and rye absorb more water, so they tolerate higher hydration

      Flour protein content matters as much as the number. A strong bread flour handles 80% comfortably where a weak all-purpose flour turns to soup at the same figure.

      Common questions

      What is baker's percentage?

      A way of expressing every ingredient as a percentage of the total flour weight, which is always 100%. It makes recipes scale cleanly to any batch size and lets two recipes be compared directly regardless of quantity.

      Should I count the starter in the hydration?

      For a true figure, yes. A 100% hydration starter is half flour and half water, and both belong in the totals. Many published recipes ignore it, which is why the same dough gets described with different hydration figures.

      How much salt should sourdough have?

      Around 2% of total flour weight. Below 1.5% fermentation runs fast and the flavour falls flat; above 2.5% fermentation slows and the crumb tightens noticeably.

      What hydration should a beginner use?

      Between 65% and 70%. It is far easier to shape, still produces a good loaf, and lets you learn the feel of properly developed dough before adding the difficulty of a slack, sticky one.

      My starter is a stiff one — does that change things?

      Yes. A 50% hydration starter is two parts flour to one part water, so 150 g contributes 100 g of flour and only 50 g of water. Set the starter hydration field accordingly or the water calculation will be wrong.

      Where these numbers come from

      Last verified 2026-08-01 The method on this page is checked against the sources above at least once a year. Spotted something out of date? Tell us and we will fix it.

      Related calculators

      Price per kg to lb

      Compare shelf prices when one is per kilogram and the other is per pound.

      Open calculator

      Epoxy resin calculator

      Work out epoxy volume from area and depth, split into resin and hardener.

      Open calculator

      Audiobook speed

      Finishing time at any playback speed, and how much you actually save.

      Open calculator

      pH calculator

      Convert between pH, pOH and hydrogen or hydroxide ion concentration.

      Open calculator

      ✨ Everyday and leisure calculators

      The small calculations that come up in a kitchen, a supermarket aisle or a games session.

      See all 10 calculators in this section