Sourdough Timer — Tell Your Bread When to Be Ready

If you've baked sourdough for more than a few weeks, you know the real problem isn't the recipe. It's the timing. When do you feed the starter so it peaks at the right hour? How do you know your levain is ready? When should you start the bulk fermentation if you want fresh bread by 7am? A sourdough timer that just counts down minutes can't answer any of these. S.D Timer can.

The Sourdough Timer Built Around Real Fermentation Science

Most timer apps treat sourdough like a recipe with fixed durations. They give you a hardcoded "feed your starter 6 hours before mixing." That works exactly never, because fermentation rate depends on conditions that change every day.

S.D Timer is different. It takes five inputs that actually affect fermentation — target bake time, ambient temperature, dough hydration, flour type, and your starter's specific activity — and calculates the timing backward. You tell the app when you want fresh bread; it tells you exactly when to feed, when to mix, when to fold, when to shape, and when to bake.

How the Sourdough Timer Calculates Your Schedule

Behind the simple interface is empirically calibrated fermentation math. The core principle: fermentation rate scales exponentially with temperature (Q10 ≈ 2 — every 10°C doubles the rate), non-linearly with inoculation ratio, and per-flour-type with documented multipliers.

The Temperature Lever

Yeast and lactic acid bacteria activity follows Arrhenius kinetics. At 22°C a 1:5:5 starter feed typically peaks in 8 hours. At 28°C the same feed peaks in 4 hours. At 18°C it takes 14+ hours. The app uses a temperature input as the foundation of every calculation. Even a 2°C difference between summer and winter shifts your schedule by an hour.

The Inoculation Ratio Lever

Higher ratio (1:1:1, 1:2:2) means more existing yeast, faster peak. Lower ratio (1:5:5, 1:10:10) means more dilution, longer lag, slower peak — but also more flavor development. S.D Timer either accepts a fixed ratio you specify, or solves for the ratio that hits your target time given everything else.

The Flour-Type Lever

Whole grain flours have higher amylase activity, more minerals, and natural microbial flora that all accelerate fermentation. The multipliers built into S.D Timer:

• White bread flour: 1.0× baseline
• Spelt: 1.35× faster
• Whole wheat: 1.5× faster
• Rye: 2.0× faster

For blends (e.g. 80% white + 20% whole wheat), the app uses a mass-weighted blended multiplier.

The Difference Between a Sourdough Timer and a Kitchen Timer

Why Bakers Use S.D Timer Instead of Spreadsheets

You can do the math in a spreadsheet. Many bakers do. But every time conditions change — a cooler kitchen, a different flour, a friend asking for bread at a specific time — you have to rebuild the formulas. S.D Timer abstracts all of that: change one input, see the entire schedule update.

It also handles edge cases that home spreadsheets usually skip:

• Cold retard schedules. Working a fridge retard into the math is non-trivial (yeast slows ~10×, bacteria slow only ~5× at 4°C). The app accounts for this.
• Mid-ferment temperature changes. If your dough sits at 24°C for the first 3 hours then drops to 20°C overnight, the schedule should adjust. Most spreadsheets assume constant temperature.
• Multi-loaf parallel timing. Baking two loaves at different hydrations? The app can handle parallel schedules.

What People Actually Use the Sourdough Timer For

Predictable morning bakes

The most common use case: "I want fresh bread Sunday at 7am." The app calculates the entire backward chain — late-night feed, mid-morning Saturday mix, afternoon bulk, evening shape, overnight cold retard, early Sunday morning bake.

Scheduling around real life

Set a target time that fits your schedule, not the other way around. Have a 9am meeting Saturday? Plan the mix for Friday night. Going out Friday evening? Use a 1:10:10 feed earlier in the day to stretch the levain peak window.

Teaching workshops

Professional baking instructors use S.D Timer to demonstrate how temperature and ratio change outcomes in real time. Change the temperature input from 22°C to 26°C — watch the entire schedule compress before students' eyes.

Seasonal recipe adjustment

The same recipe in January (kitchen 18°C) and July (kitchen 28°C) needs different timing. The app handles this transparently. No mental math required.

Sourdough Timer FAQ