HourDough
How HourDough works — a sourdough schedule calculator & starter guide
HourDough is a free sourdough schedule calculator. Tell it when you want the loaf out of the oven and your kitchen temperature, and it reverse-computes every step of the bake — when to feed the starter, when to mix the dough, when to fold, when to shape, when to cold-proof, and when to put the dutch oven in. Everything adjusts for kitchen temperature using a fermentation model that captures how sourdough actually behaves.
How the sourdough schedule calculator works
Sourdough doesn't run on a clock — it runs on temperature. Yeast and bacteria activity roughly doubles for every 10°F warmer (the standard Q10 = 2 fermentation model used in baker references). HourDough applies that across every stage: starter peak time, bulk fermentation duration, counter proof, even the float-test window for new starters.
For a single bake you enter:
- When you want the loaf out of the oven — the fixed point everything reverse-computes from.
- Your counter or table temperature — where the dough will actually sit, not what the thermostat reads.
- Three style sliders: sourness, crumb openness, crust crackliness.
- Cold proof in the fridge, on or off.
The app computes the full timeline working backward from your target ready-time. You see exact clock times for: feed-the-starter window, float-test window, mix dough (with autolyse), four stretch-and-folds 30 minutes apart, pre-shape, final shape, proof (cold or counter), oven preheat, score and bake covered, remove lid, and loaf ready.
The recipe also adjusts live with the sliders. Hydration shifts between 65 and 82 percent; whole-grain flour ramps up to 100 g for a tangier result; bake temperature ranges 455 to 485°F; uncovered time runs 18 to 30 minutes for a softer or shatteringly crisp crust.
Building a sourdough starter from scratch
The New Starter tab walks you through creating an active sourdough starter from flour and water, with no commercial yeast. The day-by-day routine:
- Day 1 (mix): 50 g whole-wheat or rye flour + 50 g room-temp filtered water in a clear jar. Stir to a thick paste. Loosely cover.
- Day 2 (first signs): stir. No feed. Possibly a few bubbles.
- Day 3 (first real feed): discard all but 50 g, add 50 g bread flour + 50 g water. Mark the jar level with a rubber band.
- Day 4 (twice-a-day rhythm starts): switch to feeding every 12 hours. Discard down to 25 g, add 50 g flour + 50 g water (a 1:2:2 feed).
- Day 5 (should be rising): same feed, same 12-hour rhythm. The starter should be doubling between feeds.
- Day 6 (float-test eligible): after the morning feed, try the float test once the rise roughly doubles.
- Day 7+ (bake-ready): once the float test passes reliably for two consecutive feeds, you can bake. Maintain at 1:5:5 (10 g starter + 50 g flour + 50 g water) once daily on the counter, or weekly in the fridge.
You enter when you mixed your Day 1 starter, and every day card shows its concrete clock times for the morning and evening feeds. Day 6 includes a temperature-scaled float-test window so you know roughly when to start checking.
The float test, explained
The float test is the standard "is my sourdough starter ready" check. Once the starter is reliably doubling between feeds, scoop a teaspoon off the top (don't stir it in first), drop it into a glass of room-temperature water, and watch:
- Floats high and confidently: your starter is at peak activity. Use within the next few hours, or feed once more and use after the next peak.
- Sinks slowly: not quite there. Wait an hour and try again.
- Sinks like a stone: either too early (not enough gas yet) or too late (the peak already passed). Feed and try after the next rise.
For Day 6 specifically, HourDough computes a temperature-scaled window where the float test should start working — roughly 6 to 12 hours after the morning feed at 75°F kitchen temperature, longer in a cool kitchen and shorter in a warm one.
Kitchen temperature is the hidden variable
The most common reason a home sourdough bake fails — overproofed or underproofed dough — is mistiming the bulk fermentation. The number on your thermostat is rarely the temperature where the bowl actually sits:
- A granite or marble counter on an exterior wall in winter can be 8°F colder than the air.
- The top of the fridge runs warmer because of compressor heat.
- A counter near the oven during a previous bake stays warm for hours.
- Direct sun on a spot through a window can shift it 5°F or more.
HourDough asks for the temperature at the spot where the bowl will sit. Measure it with a digital probe held a few inches above the counter for 60 seconds, or aim an infrared thermometer at the counter surface — both get you within a degree. A 4°F miss on input is roughly a 30 percent miss on output: the difference between a 5-hour bulk and a 6.5-hour bulk.
What HourDough doesn't do
- It doesn't replace touching the dough. The schedule is a calibrated suggestion; the final read is always the poke test, the windowpane test, the smell, the rise.
- It doesn't track your bake history. The current plan saves locally to your device only.
- It doesn't show ads.
- It doesn't have a backend. All math runs in your browser. No accounts, no servers, no tracking.
Frequently asked sourdough questions
How long does sourdough bulk fermentation take?
At 75°F kitchen temperature, a 70% hydration boule with active starter takes about 5 hours of bulk fermentation. At 65°F it roughly doubles to 10 hours. At 85°F it halves to ~2.5 hours. The standard Q10 = 2 fermentation model: yeast and bacteria activity doubles for every 10°F warmer.
When should I feed my sourdough starter for a morning bake?
Roughly 8 hours before you mix the dough, at 75°F. Cooler kitchen: more like 12 hours. Warmer: 4 to 6 hours. The HourDough calculator computes the exact starter feed window from your desired ready-time and your counter temperature.
How do I know when my sourdough starter is ready to bake with?
The float test: a teaspoon of unstirred starter dropped in room-temperature water should float high and confidently. Also: the starter should double 4 to 8 hours after a 1:5:5 feed and smell pleasantly tangy — fresh yogurt with a hint of apple.
Should I cold proof my sourdough?
Cold proof is recommended for most home bakes. The fridge slows fermentation while enzymes continue to develop flavor (especially lactic acid), making the loaf tangier and more complex. It also firms the dough so scoring is easier and gives you a flexible bake window — 8 to 20 hours in the fridge instead of a tight 2-hour counter window. HourDough defaults to cold proof on; uncheck the toggle for a same-day counter proof.
What hydration should I use for sourdough?
Depends on the loaf you want. 65% hydration produces a tight, even crumb that slices cleanly. 70 to 75% is balanced — some open holes, structurally sound. 80%+ is open crumb with big windowpanes; the dough is wetter and shaping needs to be gentler. HourDough's Crumb slider sets this anywhere from 65 to 82%.
How long does a sourdough starter take to build from scratch?
Typically 5 to 8 days from flour-and-water mix to a bake-ready, reliably-floating starter. The first three days you watch for any bubbling. Day 3 is the first real feed. Days 4 to 6 you switch to feeding every 12 hours. By Day 6 or 7 the float test should pass.
Why does the kitchen temperature matter so much?
Sourdough doesn't run on a clock — it runs on temperature. A 4°F miss on input is roughly a 30% miss on output: the difference between a 5-hour bulk and a 6.5-hour bulk. The most common reason a home sourdough bake fails is mistiming the bulk fermentation. HourDough asks for the temperature at the spot where the bowl will actually sit, not what the thermostat reads.
Is HourDough free?
Yes. Free, ad-free, no account required, no tracking, works offline once loaded. The code is on GitHub.
Try the calculator
The fastest way to understand HourDough is to use it. Enter a target ready-time, enter your kitchen temperature, drag the style sliders, and watch the full schedule render. Install it to your phone's home screen with Safari → Share → Add to Home Screen for a kitchen-side companion that works offline.
Open the HourDough calculator →