Sourdough hydration is just the ratio of water to flour in your dough, written as a percentage. A loaf at 75% hydration has 750 g of water for every 1,000 g of flour — that's it, that's the whole sum. Most UK home bakes sit between 70 and 78%. Push to 85% and you get a lacy, open crumb but a slack, sticky dough; drop to 65% and you get a tighter loaf with stronger oven spring. We'll show you which to pick.
What Sourdough Hydration Actually Is (And the Maths Behind It)
What is sourdough hydration?
Sourdough hydration is the weight of water in a loaf divided by the weight of flour, expressed as a percentage. A dough with 1,000 g of flour and 750 g of water is 75% hydration. The number tells you, at a glance, how slack the dough will feel, how open the crumb will be, and how much oven spring you can expect. It's the single most useful number on a sourdough recipe.
The one-line definition
Hydration = water ÷ flour × 100. Both measured in grams. Just a ratio.
The baker's-percentage formula, written out
Bakers express every ingredient as a percentage of total flour weight. Flour is always 100%. Water at 75% of flour weight = 75% hydration. Salt at 2% = 20 g per 1,000 g flour. Forkish lays this out in Flour Water Salt Yeast Chapter 3 — once you see it, you can scale any recipe up or down without rewriting it.
What "100% hydration" means for a starter (and why it's a different number)
A "100% hydration starter" has equal weights of flour and water — feed 20 g starter with 20 g flour and 20 g water, and the starter is 100% hydration. Don't confuse that with dough hydration: the dough has separate flour and water totals, plus whatever you inherit from the starter, all summed.
How to Calculate Hydration (The Worked Example)
A 500 g flour / 350 g water loaf
350 ÷ 500 = 0.70 = 70%. The simplest sum in baking.
Counting the starter in the sum (the bit most guides skip)
If you also add 100 g of 100% hydration starter to that loaf, half of it (50 g) is flour and half (50 g) is water. So total flour = 550 g, total water = 400 g. Hydration = 400 ÷ 550 = 72.7%. The recipe calls itself "70%" but the dough you're handling is 72.7%. Small number, real difference.
Common UK home-bake recipes and their real hydration
Most published "75% sourdough" recipes work out to 76–78% once the starter weight is added properly. BBC Good Food's white sourdough is closer to 76%; Forkish's Saturday White is 78% when you count the levain; Vanessa Kimbell's "everyday loaf" runs around 72%.
Hydration Calculator
Hydration Calculator
Slide your flour and water — including any from the starter — to see the percentage live.
65%, 75%, 80%, 85% — What Actually Changes
Crumb structure (tight to lacy)
How does hydration affect sourdough crumb?
Hydration is the strongest single lever on sourdough crumb. Lower-hydration doughs (65–70%) produce a tight, even crumb with small uniform holes — ideal for sandwiches. Mid-hydration (72–76%) gives a balanced open crumb with mixed hole sizes. Higher hydration (78–82%) produces the lacy, irregular crumb you see in artisan photos. Above 85%, the crumb can become gummy if fermentation isn't perfectly matched to the extra water.
Hydration → crumb shape
Oven spring (the height your loaf gains in the oven)
Lower-hydration loaves spring taller. A 70% loaf might gain 30% in volume in the first 10 minutes; an 82% loaf gains 20% but spreads outward. If you want a tall loaf, drop the hydration; if you want an open crumb, raise it. You can't have both.
Crust thickness and colour
Higher hydration = thinner, crackly crust because the steam from the wetter dough hits the lid of the Dutch oven harder. Lower hydration gives a thicker, more bread-y crust.
How the dough feels in your hands
65%: dense, dry, like proper bread dough. 75%: tacky-but-handleable, sticks to your fingers but releases with a light dust of flour. 82%: properly slack, needs wet hands, drips off the bowl scraper.
How Hydration Interacts with UK Flour Brands
UK strong white bread flour absorbs less water than US bread flour because it's lower in protein (12–14% vs 13–15% US). Same recipe, same hydration on paper, different dough in your hands. Elaine Boddy's bake logs and the Sourdough Hub's Somerset kitchen records both show the same pattern: UK brands cluster slightly below US numbers.
| UK flour | Protein | Style | Optimal hydration | Best loaf type |
|---|---|---|---|---|
| Marriage's Finest Strong White | 13.5% | Roller-milled | 72–76% | Country loaf, tin loaf |
| Shipton Mill Organic No. 1 | 14% | Stoneground | 74–78% | Open-crumb boule |
| Doves Farm Strong White | 12% | Roller-milled | 68–72% | Sandwich tin loaf |
| Allinson's Strong White | 12.5% | Roller-milled | 70–74% | Everyday Dutch-oven loaf |
| Wessex Mill Strong White | 13% | Stoneground | 72–76% | Country loaf |
| Bacheldre Wholemeal | 13% | Stoneground | 78–82% | Wholemeal everyday loaf |
| Gilchesters Strong White | 14% | Stoneground | 74–78% | Show-off open crumb |
Marriage's strong white — happiest at 72–76%
The UK home-baker workhorse. 13.5% protein, predictable absorption. Start at 72% for a first loaf; nudge to 76% once you've baked a few.
Shipton Mill organic — likes 74–78%
Slightly higher protein, stoneground. Handles more water without going slack. The flour we reach for when we want open crumb.
Doves Farm strong white — drop to 68–72%
Lower protein than Marriage's. A "75% recipe" with Doves Farm will feel like 78% in your hands. Drop the water 30–40 g and the dough behaves.
Wholemeal, rye and spelt — add water, not subtract
Bran absorbs more water than white flour. A 20% wholemeal blend needs ~2 percentage points more hydration than all-white; a 50% wholemeal needs 5–6 pp more. Pure rye drinks water like sand — 80%+ is normal.
A UK flour absorption table
See the table above. For every gram of flour you swap white-for-wholemeal, add ~0.05 g water. For every gram of rye, add ~0.1 g. Boddy's Whole Grain Sourdough at Home covers this in more detail.
How Hydration Behaves at UK Kitchen Temperatures
Why a warm kitchen makes the same dough feel wetter
Warmer flour absorbs less water, warmer dough relaxes faster, warmer gluten holds less structure. A 75% dough mixed at 8 am in a 17°C January kitchen feels firm and shapeable by lunchtime. The same dough at the same hydration in a 23°C July kitchen feels like 80% by lunchtime — slack, sticky, harder to handle.
The Met Office baseline — what UK kitchens actually run at
Met Office UK climate averages give Somerset (a representative central-southern data point): January monthly mean 6.4°C → typical kitchen 16–18°C; July monthly mean 16.8°C → typical kitchen 21–24°C. Most UK home bakers swing through an 8°C kitchen range over the year. The same recipe behaves differently in February than it does in July.
A practical adjustment ladder by month
Nov–Feb (kitchen 16–18°C): bake at the stated hydration. Mar–Apr / Oct (kitchen 18–20°C): bake at the stated hydration. May / Sep (kitchen 20–22°C): drop 1 pp if the dough feels slack. Jun–Aug (kitchen 22–24°C): drop 2 pp, or chill the water before mixing. The flour can wait. Your kitchen can't.
How to Tell If Your Dough Is Too Wet or Too Dry
Six tactile signals (with what to do about each)
What hydration should a beginner start with?
Start at 70% for your first sourdough loaf, not 80%. Seventy per cent gives you a dough you can shape on a lightly-floured bench, a forgiving bulk ferment, and a crumb that bakes reliably even when timings drift. Once you've baked three or four good loaves at 70%, nudge to 72%, then 75%. Each step up makes the dough slacker and rewards better handling. The flour can wait.
- Dough won't form a ball — too wet. Add 10 g flour, knead briefly.
- Dough rips when stretched — too dry. Add 10 g water by dimpling.
- Dough feels like wallpaper paste — too dry, plus over-kneaded.
- Dough drips off the spatula — well above 80%. Knead in 20 g extra flour or accept and bake.
- Dough holds its shape but feels heavy — under 68%. Nudge water up next time.
- Dough feels tacky-but-releases — you're at the sweet spot for that flour.
The windowpane and the slack-stretch tests
Take a piece of dough, stretch it between your fingers. If it forms a thin translucent window without tearing, gluten is developed and hydration is well-matched. If it tears immediately, either hydration is wrong or the dough hasn't been worked enough.
What "shaggy" looks like vs "soupy"
Shaggy = rough, lumpy, slightly sticky, holds together when scraped. Soupy = pourable, leaves a wet trail, drips off the spoon. Shaggy is right at 30 minutes after mix. Soupy means you went too far.
Hydration Troubleshooting (Sticky, Tight, Won't Shape)
It's gluing to my hands and won't form a ball
Hydration too high for the flour, or kitchen too warm. Wet your hands instead of flouring them — the dough sticks to itself more than to wet skin. Next time, drop 20 g water.
It's so tight I can't stretch and fold
Under-hydrated, or over-floured during shaping. Wet your hands, sprinkle 10 g water across the surface, dimple it in. Wait 10 minutes. Try again.
It looks great in the bowl, collapses on the bench
Probably over-hydrated for your flour. The bowl supports the slack dough; the bench doesn't. Either drop hydration next time, or do a longer cold retard to firm the structure before shaping.
It rose beautifully but came out gummy
Over-hydration + under-bake. The water didn't fully evaporate during the bake. Either drop 2 pp hydration, or bake 5 minutes longer at the lid-off stage and check for the 96°C internal temperature.
Hydration Sweet Spots for Common UK Loaves
What's the ideal hydration for sourdough bread?
There's no single ideal — it depends on the flour and the loaf you want. For a beginner-friendly UK bake with strong white flour, 70 to 72% is reliable. For a balanced open-crumb country loaf, 74 to 76% is the sweet spot. For a lacy, show-off crumb, push to 78 to 82%, but only once you've handled wetter dough. Wholemeal and rye need more water, not less.
70–72%Tin loaf for sandwiches. Even crumb, sliceable, holds butter.
74–76%Dutch-oven country loaf. The home-baker sweet spot.
78–82%Open-crumb show-off bake. Wet-hands shaping.
80%+Wholemeal everyday loaf, or rye-heavy bake.
Is 75% hydration sourdough high?
No — 75% hydration sourdough is moderate, not high. It sits squarely in the home-baker sweet spot for strong white flour, gives a balanced open crumb, and is well within what a beginner can handle. High hydration in home-baking terms starts around 80%, where the dough becomes properly slack and needs wet-hands shaping. Very high (85%+) is for experienced bakers with strong UK flour and a confident bench technique.
Clara: "I still work at 72% for everyday loaves. Nothing fancy, just reliable. I push to 76% for the loaf that gets a photo on Instagram. I've baked at 85% maybe ten times in my life. You don't need wet dough to make good bread."
Hydration vs crumb-hole size by flour type
Hub bake logs (Somerset, n=142) cross-referenced with Modernist Bread hydration tables. Wholemeal peaks higher and earlier than white; rye plateaus low across the range.
Frequently asked questions
What is sourdough hydration?
Sourdough hydration is the weight of water in a loaf divided by the weight of flour, expressed as a percentage. A dough with 1,000 g of flour and 750 g of water is 75% hydration. The number tells you, at a glance, how slack the dough will feel, how open the crumb will be, and how much oven spring you can expect. It's the single most useful number on a sourdough recipe.
What's the ideal hydration for sourdough bread?
There's no single ideal — it depends on the flour and the loaf you want. For a beginner-friendly UK bake with strong white flour, 70 to 72% is reliable. For a balanced open-crumb country loaf, 74 to 76% is the sweet spot. For a lacy, show-off crumb, push to 78 to 82%, but only once you've handled wetter dough. Wholemeal and rye need more water, not less.
Is 75% hydration sourdough high?
No — 75% hydration sourdough is moderate, not high. It sits squarely in the home-baker sweet spot for strong white flour, gives a balanced open crumb, and is well within what a beginner can handle. High hydration in home-baking terms starts around 80%, where the dough becomes properly slack and needs wet-hands shaping. Very high (85%+) is for experienced bakers with strong UK flour and a confident bench technique.
How does hydration affect sourdough crumb?
Hydration is the strongest single lever on sourdough crumb. Lower-hydration doughs (65–70%) produce a tight, even crumb with small uniform holes — ideal for sandwiches. Mid-hydration (72–76%) gives a balanced open crumb with mixed hole sizes. Higher hydration (78–82%) produces the lacy, irregular crumb you see in artisan photos. Above 85%, the crumb can become gummy if fermentation isn't perfectly matched to the extra water.
What hydration should a beginner start with?
Start at 70% for your first sourdough loaf, not 80%. Seventy per cent gives you a dough you can shape on a lightly-floured bench, a forgiving bulk ferment, and a crumb that bakes reliably even when timings drift. Once you've baked three or four good loaves at 70%, nudge to 72%, then 75%. Each step up makes the dough slacker and rewards better handling. The flour can wait.
Why does my dough feel different in summer?
Warmer flour absorbs less water, warmer dough relaxes faster, warmer gluten holds less structure. A 75% dough in a 17°C January kitchen feels firm; the same recipe in a 23°C July kitchen feels like 80%. Drop 2 percentage points hydration in high summer, or chill the water before mixing.
Does the starter count in the hydration sum?
Yes — and most published recipes ignore it. A 100% hydration starter is half flour, half water by weight. Add 100 g starter and you're adding 50 g flour and 50 g water to your totals. A recipe that calls itself "70%" often turns out to be 72–73% once you do the maths properly. Small difference, real effect.
What's next
If your bulk fermentation feels off — too fast, too slow, hard to read — the UK bulk-ferment and cold-retard timing guide covers the matched-pair to hydration. If a loaf came out flat, dense or gummy, the universal troubleshooter for flat, dense or gummy loaves walks the diagnosis. And for knowing when dough is actually ready to bake, the poke test for knowing when dough is ready is the most useful diagnostic you'll learn.
The pillar that ties it all together: our complete beginner's guide to your first sourdough loaf.
Sources: Forkish, Flour Water Salt Yeast, 2012; Myhrvold & Migoya, Modernist Bread, 2017; Boddy, FoodBod Sourdough; Met Office UK Climate Averages 1991–2020; Sourdough Hub Somerset bake logs 2025–2026.
