How to calculate sourdough hydration and baker's percentage

Sourdough hydration is water weight divided by flour weight, written as a percentage. A dough of 500g flour and 350g water is 70%. Most home formulas state that number too low, because they leave the starter's own flour and water out of the arithmetic.

How to calculate baker's percentage

Total flour is always 100%, and every other ingredient is expressed against it: ingredient weight ÷ total flour weight × 100. Water at 70% means 70g of water per 100g of flour. The percentages don't sum to 100, and their total is the part people forget to use.

A plain country formula:

• 500g bread flour — 100%
• 350g water — 70%
• 100g starter — 20%
• 10g fine salt — 2%

Those add up to 192%, and the dough weighs 960g. To scale, work backward from the dough weight you want: 1,000 ÷ 1.92 = 521g flour, then 365g water, 104g starter, and 10g salt. That portability is why baker's percentage sourdough formulas survive being passed around and cup measurements don't.

Your starter is flour and water, and the totals should say so

Here's the step most recipes skip. A 100% hydration starter — what a 1:1:1 feed produces — is half flour and half water by weight. The 100g of starter above is 50g of flour and 50g of water hiding inside one line item.

Fold it in:

• True flour: 500 + 50 = 550g
• True water: 350 + 50 = 400g
• True hydration: 400 ÷ 550 = 72.7%, not 70%
• True salt: 10 ÷ 550 = 1.8%, not 2%

Two to four points is typical, and the gap widens as you use more starter: with a 100% starter, each extra 10% of inoculation adds roughly 1.3 points of real water.

Now run the identical recipe with a stiff 50% hydration starter. That 100g is 66.7g flour and 33.3g water, so true flour is 566.7g, true water is 383.3g, and hydration lands at 67.6%. Same written recipe, same numbers on the scale, a five-point spread in the dough — and most of the answer to why two bakers following one formula get doughs that handle nothing alike.

The general form, with starter hydration h as a decimal:

• starter flour = starter weight ÷ (1 + h)
• starter water = starter weight − starter flour

For a 100% starter h = 1.0; for a stiff one at 50%, h = 0.5. Your starter's hydration is set by your feeding ratios.

Sourdough hydration percentage: ranges that actually work

Total hydration	How it handles	Crumb	Where it fits
60–65%	Firm, barely tacky	Tight, even	Pan loaves, rolls, weaker flour
65–70%	Tacky but shapes cleanly	Moderately open, regular	Beginner band, whole-grain blends
70–75%	Slack, wants coil folds	Open, mixed hole size	Everyday country loaf
75–85%	Loose at mix, tightens with folds	Large, irregular	Open crumb with strong flour
85%+	Nearly pourable, needs a cold retard	Very open, fragile	Ciabatta-style, experienced hands

Start at 65–70% if you're learning or working with a lot of whole grain. Move to 75–85% only once your dough passes a windowpane, because water amplifies whatever your gluten and fermentation are already doing. Adding water to an under-fermented dough gets you a gummy, flat loaf, not an open one.

The number also isn't comparable across flours. Whole wheat and rye both drink more water than white flour, for different reasons — wheat bran physically cuts gluten strands, while rye's pentosans (soluble fiber) bind extra water even though rye barely forms a gluten network at all. So a 100% whole wheat dough at 75% handles roughly like white flour in the high 60s. High-protein bread flour drinks more than all-purpose, and freshly milled flour more than flour that's been sitting. Let the percentage be the record of what you did, not the target you chase.

Sourdough salt percentage

Use 1.8–2.2% of total flour, with 2% as the default. Salt tightens gluten and slows fermentation, so it's doing structural work, not just seasoning. Below about 1.5% the dough goes slack and the bread tastes flat; above about 2.5% fermentation drags and the crumb tightens.

Calculate it against total flour, starter included — that's what turned the 2% above into 1.8%. Weigh it, too — a tablespoon of coarse kosher salt and a tablespoon of fine sea salt are nowhere near the same weight.

How much starter to use in sourdough

Inoculation is starter weight ÷ flour weight. Most formulas sit between 10% and 20%, and some write the sourdough inoculation percentage against total flour instead of added flour, so check which convention a recipe uses before copying its number.

This lever controls speed more than flavor. At a dough temperature around 76–78°F (24–26°C), a healthy starter at 20% usually finishes bulk in roughly 4–5 hours; at 10%, expect closer to 6–8. Lower inoculations stretch the clock and give acids more time to develop, which reads as a tangier loaf, but they punish a sluggish starter. If yours takes more than about 6 hours to peak after a feed, fix that before dropping the inoculation — the float test is a rough check, and a starter that peaks predictably is worth more than any percentage.

Dough temperature moves the timeline harder than inoculation does. A few degrees warmer can pull an hour out of bulk, which is why the same 15% inoculation behaves like two different recipes in January and July.

Change one lever at a time

Hydration, inoculation, salt, and temperature all push on fermentation, so moving two at once tells you nothing. Change one, note the dough temperature at the end of mixing, note the bulk length, and cut the loaf. Sourdough Tracker is a sourdough baking companion app for iPhone, and keeping a per-bake record like that is what makes a hydration change readable instead of a guess — the numbers only teach you something sitting next to the timings of the same loaf.

FAQ

Does the starter count toward sourdough hydration?

It should. A 100% hydration starter is half flour and half water, so 100g of it adds 50g to each side of the ratio. Folding it in typically raises a stated hydration by 2–4 points, and a stiff starter lowers it instead.

What hydration should I start with?

65–70% with bread flour. It's tacky enough to build strength through folds but still shapes cleanly, so you learn what fermented dough feels like before water hides your mistakes.

Why is my 80% hydration dough soupy when someone else's isn't?

Flour and starter, usually. Their flour may absorb more, their starter may be stiff where yours is liquid, and their real hydration may sit several points below the number they wrote down. Under-fermentation and warm dough also read as slackness.

Should salt be calculated on total flour or just the added flour?

Total flour, including the flour inside your starter. That's the convention professional formulas use, and it keeps the salt percentage honest as you change inoculation.

How do I convert a cup-based recipe to baker's percentage?

Weigh everything once as you make it, then divide each weight by the total flour weight. Cup volumes vary widely depending on how the flour was scooped, so a converted recipe is only as good as the bake you weighed. Building a starter from scratch helps here, since you'll know its hydration exactly.