Gilligan's Sourdough Calculator

Work out a dough formula in grams from baker's percentages, feed your starter the right amount, nail your water temperature, and keep a log of feeds and bakes — all in one place.

Your formula

Everything is a baker's percentage of the flour. Change anything and the grams on the right update instantly.

Flour blend

Blend totals 100% — good.

Inclusions (% of flour weight)

Weigh-out

800 g of dough in 1 loaf.

IngredientBaker's %TotalPer loaf

Feed the jar

Tell it what you're keeping and the feeding ratio — it works out the flour and water, and how much discard comes off the top.

A higher ratio means a smaller share of old starter, so the feed takes longer to peak — handy for overnight or fridge timing. A starter kept at room temperature usually wants feeding once or twice a day; in the fridge, about once a week.

A jar of active sourdough starter, bubbly and risen

Build a levain for a bake

Work backwards from the levain your formula calls for. Pick a ratio and it splits into seed starter, flour and water.

Use up the discard

Discard is just unfed starter — don't bin it. Enter what you've got and these recipes rescale to match.

No-Discard Mode

The trick is rhythm, not storage. If you bake about twice a week, you never need a discard step at all: each feed is the levain for the next bake, and all that's left in the jar afterwards is a small carryover that seeds the feed after that. Nothing gets thrown away — the starter just cycles from bake to bake.

"A starter is like a cat — the feeding is why people rehome them. Bake twice a week, and the feeding has a purpose."

How the cycle works

  1. Bake day, the night before
    Feed the whole jar

    Take the small carryover sitting in the jar and feed it up to exactly the levain your next formula needs, using the amounts on the right.

  2. Bake day morning
    Bake with nearly all of it

    Pour the risen levain into your dough — but scrape just the carryover amount back into the jar first (or leave that much behind). That little bit is your starter now.

  3. Between bakes
    The carryover waits

    A small amount of starter keeps happily in the fridge for the few days until the next bake. Small is good: less old starter in the next feed means a fresher, less acidic levain.

  4. Next bake, 3–4 days later
    Feed again, bake again

    Same move, every time. Feed the carryover up to the levain you need, bake, keep the carryover. Twice a week is the sweet spot — the fridge stretch stays short enough that the starter never gets sluggish or overly sour.

Going longer than about a week between bakes? Give the carryover one small refresh feed (even 1 : 1 : 1 with a spoonful each of flour and water) mid-gap, or accept one discard feed to perk it back up. And if you bake less often than that, the regular Discard & Feeding tab is the better tool.

Work out the feed

Enter the levain your formula calls for and your feed ratio. You'll get the carryover to keep and the flour and water to add — they add up to exactly your levain, with nothing left over.

Water temperature

Dough temperature drives fermentation speed. Measure flour, room and levain, pick your target, and this works out how warm the mixing water should be.

Mixing warms dough up — that's the friction factor. The formula multiplies the desired dough temperature by four (flour, water, room and levain), subtracts the three temperatures you measured and the friction, and what's left is the water temperature.

Hands kneading dough on a floured surface

Use water at

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Rule of thumb

Most sourdough behaves best finishing mixing at 75–78 °F (24–26 °C). A couple of degrees warmer and bulk fermentation speeds up noticeably; cooler and everything slows down — which is sometimes exactly what you want before an overnight fridge proof.

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New to sourdough? Start here.

Sourdough is just flour, water, salt and time. A small jar of starter — flour and water colonised by wild yeast and friendly bacteria — does all the lifting that a packet of yeast does in other breads. You feed the starter, mix it into a dough, let the dough rise slowly, shape it, and bake it hot. That's the whole craft; everything else is refinement.

Work in baker's percentages: flour is always 100%, and every other ingredient is a percentage of the flour weight. The classic loaf in the Dough Calculator — 800 g total, 65% water, 20% levain, 2% salt — is a forgiving place to begin. Weigh everything in grams, trust the scale over the clock, and watch the dough, not the timer.

A sliced sourdough loaf showing an open, airy crumb and a deep golden crust

Bake day, step by step

Timings are a guide for a kitchen around 72 °F (22 °C). Warmer dough moves faster; cooler dough slower.

  1. The night before
    Feed the levain

    Use the Discard & Feeding tab to build the levain your formula calls for — for the classic loaf that's about 96 g. Leave it at room temperature overnight so it's bubbly and just peaking in the morning.

  2. Morning · 10 min
    Mix

    Whisk the levain into the water (use the Dough Temperature tab to get that water temperature right), add the flours, and mix to a shaggy mass with no dry flour left. Add the salt with a splash of held-back water, and work it in until the dough comes together.

  3. 30–60 min
    Rest

    Cover and leave the dough alone. The flour hydrates, the gluten starts forming on its own, and the dough becomes much easier to handle.

  4. Over the next 2 hours
    Stretch and fold

    With a wet hand, pull one side of the dough up and over the middle; turn the bowl and repeat four times. Do a set every 30 minutes or so. The dough should turn smooth, elastic and noticeably stronger.

  5. 3–5 hours total
    Bulk fermentation

    Leave the covered dough to rise until it's grown by roughly half to three-quarters, looks pillowy, and shows bubbles at the surface. This is the step that decides flavour and crumb — ending it too early is the most common beginner mistake after ending it too late.

  6. 20 min
    Shape

    Tip the dough onto a lightly floured surface, fold it into a parcel, rest it seam-down for 20 minutes, then shape it tightly into a round or oval and place it seam-up in a floured basket or a towel-lined bowl.

  7. 8–14 hours
    Cold proof

    Cover and refrigerate overnight. The cold slows the yeast but not the flavour, firms the dough up for scoring, and means fresh bread whenever you choose to bake the next day.

  8. Next day · 45–50 min
    Bake

    Heat the oven with a Dutch oven inside to 500 °F (260 °C). Turn the loaf onto parchment, score the top with a lame or sharp knife, and bake 20 minutes with the lid on, then 20–25 minutes with the lid off at 450 °F (230 °C), until deeply golden.

  9. At least 2 hours
    Cool, then slice

    The loaf is still finishing inside as it cools. Cutting early makes the crumb gummy, however good it smells. Log the bake in the Tracker while you wait — notes on what you'd change are gold next time.

Glossary

The words bakers use, in plain language.

Baker's percentage
Every ingredient expressed as a percentage of the total flour weight. Flour is always 100%, so a formula scales up or down cleanly to any loaf size.
Starter
The jar of flour and water you keep alive with regular feeds. It's home to the wild yeast and bacteria that raise your bread.
Levain
A fresh, offshoot feed of starter built for one specific bake — the amount in your formula. Same culture as the starter, made to peak right when you mix.
Discard
The portion of starter removed before a feed, so the jar doesn't grow forever. It's perfectly good food — see the discard recipes on the Discard & Feeding tab.
Hydration
The water in a dough as a percentage of the flour. 65% is firm and manageable; 75%+ is wetter, softer and gives a more open crumb — and stickier hands.
Autolyse
An optional rest after mixing just flour and water, before adding levain and salt. It hydrates the flour and starts gluten development, making the dough smoother and more extensible.
Bulk fermentation
The dough's main rise in the bowl after mixing, during which flavour develops and the dough fills with gas. Ends when the dough has grown substantially — not necessarily doubled.
Stretch and fold
A gentle way to build strength: pulling the dough up and over itself a few times instead of kneading. Done in sets during the early part of bulk fermentation.
Proofing
The shaped loaf's final rise. Sourdough is often proofed slowly in the fridge overnight (a cold proof), which deepens flavour and makes scoring easier.
Scoring
The slash cut into the top of the loaf before baking. It gives the expanding loaf a planned place to open instead of bursting at random.
Oven spring
The rapid rise in the first minutes of baking, as gases in the dough expand in the heat. A well-fermented, well-shaped loaf springs the most.
Crumb
The inside of the loaf — its hole structure and texture. An "open crumb" has varied, well-defined holes; a "tight crumb" is finer and more sandwich-like.
Dutch oven
A heavy lidded pot baked inside your oven. It traps the loaf's own steam, which keeps the crust supple long enough for full oven spring and a crisp, blistered finish.
Desired dough temperature (DDT)
The temperature you want the dough at right after mixing. Because fermentation speed is mostly temperature, hitting your DDT makes timings predictable — the Dough Temperature tab works out the water temperature to get there.