Sourdough Feeding Schedule Calculator

Introduction:

Sourdough timing is part recipe math and part fermentation watching. A feeding schedule has to produce enough ripe starter for the bake, keep a small reserve for handling losses, and make the culture reach its strongest window when the dough is ready to mix. The ingredient weights can be calculated precisely, but the clock estimate depends on a living culture.

Feeding ratios describe the weight relationship between mature starter, fresh flour, and water. A 1:1:1 feed uses equal weights of seed starter, flour, and water. A 1:5:5 build uses one part seed starter with five parts flour and five parts water, so it has much more fresh food relative to the microbes already in the jar. Higher ratios usually peak later and can suit overnight levain builds. Lower ratios peak sooner and often fit same-day maintenance or a warm kitchen.

Hydration is the second piece of ratio language. A 100% hydration starter has equal weights of flour and water, so a 1:5 feed at 100% hydration becomes 1:5:5. A 65% hydration stiff levain still uses five flour parts, but the water part is 3.25, making the displayed ratio 1:5:3.25. That difference changes both the scale weights and the way the build looks as it rises.

Peak is not a single reliable minute. A ripe starter is usually expanded, bubbly, aromatic, and still strong enough to lift dough. A starter that has fallen may add flavor but can weaken rise, while a starter used too early may not bring enough yeast activity. The most useful schedule combines calculated times with jar marks, repeated notes from the same kitchen, and visual cues from the actual build.

Starter planning also protects the mother jar. A levain build can accidentally use nearly all mature starter if the target amount, ratio, and reserve are not checked together. Good feeding math keeps the seed amount, fresh flour, water, usable starter, and remaining mother starter visible before anything is mixed.

How to Use This Tool:

Choose whether the bake is controlled by a target ready time or by a known feed time, then tune the feed around the starter you actually have.

1. Choose a Feeding profile for the closest workflow, such as overnight levain, same-day build, daily maintenance, fridge refresh, stiff levain, or custom.
2. Select the Schedule mode. Use Target ready time when you know when the starter should peak, or Feeding time when you know when the feed will happen.
   Target-ready mode works backward to a feed time. Feed-time mode projects the peak and use window forward from the entered feed time.
3. Enter Usable starter needed, then choose the Feeding ratio. Use Custom flour parts when the preset ratios do not match your formula.
4. Set Starter hydration, Kitchen temperature, Feed flour, and Starter activity. These fields affect the water weight, estimated peak time, and guidance checks.
5. Enter Mature starter available. Open Advanced when you need to adjust Build reserve, Mother starter to keep, or the Early-use threshold.
6. Review the Feeding Plan Table, Ingredient Weight Table, and Feeding Guidance Table before mixing. Use Copy formula when you want a compact feed note for the bake plan.
7. Fix any validation warning before relying on the timeline. The accepted ranges are 5 g to 5000 g usable starter, 0.2 to 30 flour parts, 45% to 150% hydration, 4 C to 40 C kitchen temperature, 0% to 30% reserve, and 60% to 98% early-use threshold.
   If the calculated feed time has already passed, feed now, warm the starter, lower the ratio, or adjust the bake schedule instead of treating the missed time as usable.

Interpreting Results:

The summary highlights the next important time. In target-ready mode, that is the calculated feed time. In feed-time mode, it is the projected peak time. The ingredient line gives mature starter seed, fresh flour, and water weights, followed by the estimated time to peak.

The Feeding Plan Table is the timing sequence: measure seed, feed the build, start checking at the early-use threshold, use near peak, and note the latest practical use. The Ingredient Weight Table is the scale workflow. It also shows whether enough mature starter remains for the mother jar or whether the build needs more seed than is available.

The Peak Timeline Chart is an estimate of rise over time, not a substitute for jar marks. Start checking at the early-use time, then use aroma, bubbles, expansion, and whether the starter is still holding near its high point before mixing dough.

Technical Details:

Sourdough feeding math starts with the final amount of usable ripe starter. A reserve is added for scale rounding, jar residue, and small readiness checks. The total build is then split into seed, flour, and water from the selected flour parts and hydration. Because the ratio is by weight, the same arithmetic works for a small maintenance feed and a larger levain build.

The timing model is deliberately approximate. It treats feeding ratio as the base timing driver, then adjusts for temperature, hydration, flour activity, and starter activity. The result is clamped to a practical 2 to 36 hour peak range. That boundary prevents extreme inputs from producing a false sense of precision, but it also means very cold storage, weak starters, and unusual flour blends still need direct observation.

Mass Formula

S is mature starter seed, T is usable starter target, r is reserve as a decimal, F is flour parts per 1 seed part, and H is hydration as a decimal. Fresh flour equals S x F. Water equals S x F x H. Total build equals usable target plus reserve.

Timing Formula

The early-use time is calculated as a percentage of the estimated peak path. The selected threshold is converted to a decimal and raised to 0.65 before multiplying by peak hours. That makes an 80% rise target occur closer to peak than a plain 80% time split, which better matches the idea that rise often accelerates before it slows near the top.

Limitations and Accuracy Notes:

Starter timing is an estimate, not a lab measurement. Flour freshness, water chemistry, jar shape, inoculation history, starter maturity, mixing temperature, and room-temperature swings can all move the real peak earlier or later than the model predicts.

• Use the schedule to plan the feed, then trust visible cues before mixing dough.
• Mark the jar level after feeding so expansion and collapse are easier to see.
• Keep notes by starter, flour, room temperature, ratio, and actual peak time; repeated local observations will beat a generic model.
• A starter that smells harsh, shows unusual discoloration, or has suspected mold should be handled as a food-safety concern rather than a scheduling problem.

Worked Examples:

Overnight levain target

A baker wants 220 g of usable starter with a 6% reserve and a 1:5 feed at 100% hydration. The total build is 233.2 g. The ratio has 1 seed part, 5 flour parts, and 5 water parts, so the seed is about 21.2 g, flour is 106.0 g, and water is 106.0 g. At 22 C with a steady starter and a mixed white-plus-whole-grain feed, the peak estimate is about 10.1 hours.

Same-day build

A same-day formula needs 180 g of ripe starter with a 5% reserve and a 1:2 feed at 100% hydration. Total build is 189 g. The ratio totals 5 parts, so the seed is 37.8 g, flour is 75.6 g, and water is 75.6 g. A warm kitchen or strong starter can make this build peak several hours sooner than an overnight 1:5 build.

Stiff levain

A 1:5 feed at 65% hydration displays as 1:5:3.25 because water is 65% of flour weight. For a 180 g usable target with a 5% reserve, total build is 189 g, seed is about 20.4 g, flour is about 102.2 g, and water is about 66.4 g. The lower hydration changes the texture and adds extra hold time in the use-window estimate.

FAQ:

Glossary:

Seed starter

Mature starter taken from the jar to inoculate the next feed.

Levain

A starter build prepared for a specific dough mix, often separate from the mother jar.

Hydration

Water weight as a percentage of flour weight.

Feeding ratio

The weight relationship between seed starter, fresh flour, and water.

Peak

The high-readiness window when the starter is expanded, active, and still able to lift dough well.

Mother starter

The ongoing starter kept after a levain or maintenance feed is measured out.

References:

• King Arthur Baking, Sourdough Starter Maintenance
• King Arthur Baking, Testing Different Sourdough Feeding Ratios
• The Sourdough Journey, Post-Pandemic Sourdough Guide