Sourdough Starter Feeding Scheduler

Using the calculator

The scheduler has three inputs. First, set the time you want your starter ready. This is when you plan to mix your dough, not when you plan to bake. Give yourself at least 30 minutes to gather ingredients after the starter peaks before it starts declining.

Next, choose your feeding ratio. If you maintain a 1:1:1 starter (equal parts old starter, fresh flour, and water by weight), that's typically ready in 4–6 hours at room temperature. A 1:5:5 build (used to create a levain for a specific bake) takes 8–12 hours.

Finally, enter your kitchen temperature. This is the single most important variable. A cold kitchen can double the time to peak; a warm kitchen can cut it in half. Use a thermometer if you have one. Estimating by feel is often off by 3–4°C.

What does "at peak" mean?

Peak is the moment of maximum fermentation activity. The starter has consumed most of the fresh flour you fed it and is at its most leavening power. Using your starter at peak produces the best oven spring, the most predictable fermentation in your dough, and the flavour profile you're aiming for.

Using it too early (under-fermented) means weaker leavening and under-developed flavour. Using it too late (past peak) means the wild yeast has run out of food, the acetic acid bacteria have become dominant, and your dough will be more sour and less airy than intended.

The peak isn't an instant. It's a window, typically 1–3 hours wide depending on your ratio and temperature. The calculator shows you that window so you can plan around it, not just hit a single target time.

How feeding ratios affect timing

A feeding ratio like 1:2:2 means one part old starter, two parts fresh flour, two parts water.all by weight. The ratio controls how much food you're giving the culture relative to the amount of existing organisms, which directly determines how long it takes to reach peak.

1:1:1 is a quick refresh. High inoculation (50% old starter) gives the culture a large head start. Peak comes fast, typically 4–6 hours. Good when you need the starter ready quickly or for daily maintenance.

1:2:2 is the most common maintenance feed. Lower inoculation dilutes the existing culture, buying you more time (6–8 hours). This is the default for bakers who feed once a day and bake the next morning.

1:5:5 and 1:10:10 are levain builds. You're creating a larger quantity of starter specifically for a single bake. These long builds (8–16 hours) develop more complex flavour and are commonly done overnight.

How temperature changes the schedule

This calculator uses the Q10 temperature coefficient. This is a well-established principle in biology that the rate of a biochemical process roughly doubles for every 10°C (18°F) increase in temperature. Applied to sourdough fermentation, it means:

At 20°C (68°F), a starter that normally peaks in 7 hours at 24°C (75°F) will take about 9–10 hours. At 28°C (82°F), that same starter may peak in just 5 hours. These aren't rough approximations. The model holds reasonably well across the typical kitchen temperature range of 18–30°C (65–86°F).

The practical lesson: don't set a feeding schedule on clock time alone. Two bakers with identical ratios in kitchens 5°C apart will see different peak times. Always factor in temperature. When seasons change or you turn on the heating, recalibrate.

How to tell when your starter is at peak

The float test (dropping a small spoonful of starter into water to see if it floats) is unreliable. What actually indicates peak:

The dome test. A starter at peak forms a domed or slightly convex surface. Before peak it's still rising and flat. Past peak it collapses and becomes concave. The dome is your target.

The rubber band trick. After feeding, put a rubber band or piece of tape at the level of the starter. Watch it rise. When it reaches its highest point before beginning to fall, that's peak.

Volume. A healthy starter will roughly double (sometimes more) between feed and peak. If yours isn't doubling, it may be under-active, or your kitchen may be cooler than you think.

Smell and texture. At peak, the starter smells pleasantly tangy and yeasty, not harsh or alcoholic (those are signs it's past peak). It should be bubbly throughout, not just on the surface.

Common feeding schedules

Baking Saturday morning at 9am. At 22°C (72°F) with a 1:2:2 ratio, peak comes in about 8 hours. Feed at 1am. Alternatively, use a 1:5:5 and feed at 9pm the night before.

Baking after work. If you're mixing dough at 6pm and your kitchen is 20°C (68°F), a 1:1:1 ratio needs feeding around noon. A 1:2:2 needs an early morning feed around 7–8am.

Weekend maintenance (not baking). Feed once a day at whatever time suits you. The starter doesn't need to be at peak for maintenance. You're just keeping it alive. Store in the fridge between bakes if you only bake weekly.

The scheduler above handles all of these scenarios. Just enter your target time and let it do the backwards arithmetic.