Sourdough Bread Calculator
Scale your sourdough recipe by number of loaves and size. Get exact grams, baker's percentages, levain amounts, and a personalized baking schedule.
🍞 Recipe Settings
⚖️ Ingredient Weights
| Ingredient | Grams | Baker's % |
|---|
📅 Suggested Baking Schedule
How the sourdough calculator works
Sourdough is really just three numbers: how much flour you start with, how much water you add relative to that flour, and how much active starter goes in. Bakers express the last two as baker's percentages — every ingredient is stated as a percentage of the total flour weight, which is always 100%. This calculator does that math backwards: you tell it the finished loaf size and the percentages you want, and it returns exact gram weights for flour, water, starter and salt.
To use it, pick your number of loaves and a target finished weight (a "medium" 750 g loaf is typical for a home batch), then set two sliders. Hydration is the water-to-flour ratio: 65–70% gives a tighter, sandwich-style crumb that's easy to shape, while 75–85% gives the open, holey crumb of an artisan loaf but a wetter, stickier dough that's harder to handle. Starter percentage controls how fast the dough ferments — more starter means a faster rise but a shorter window before it over-proofs. The tool also adds salt at the standard 2% of flour weight, which is the sweet spot for flavour and gluten strength.
Tips for reliable loaves
Weigh everything in grams — sourdough is far too sensitive for cups. Keep your salt near 2%: too little and the dough slackens and tastes flat, too much and it slows fermentation noticeably. If your kitchen is cold, lean toward a higher starter percentage or a longer proof; if it's warm, drop the starter percentage so the dough doesn't run away from you. And remember that hydration figures assume a strong bread flour — whole-grain and rye flours drink far more water, so a "72%" dough with lots of whole wheat will feel much stiffer than the same number with white flour.
Frequently asked questions
What hydration should a beginner start with?
Around 68–70%. It's forgiving to shape, holds its structure, and still bakes into a proper open loaf. Once you're comfortable, push toward 75%+ for a more open crumb.
How much starter do I really need?
Most home recipes use 15–25% of the flour weight. Less starter means a longer, slower ferment (more sour flavour); more means a faster rise. This tool defaults to 20%, a balanced middle ground.
Does the finished loaf weigh the same as the dough?
No — loaves lose roughly 10–15% of their weight as water evaporates during baking. The calculator targets your chosen finished weight and works back to the raw dough amounts, so you don't have to guess.
Why grams and not cups?
A cup of flour can vary by 20% depending on how it's scooped, which is enough to throw off hydration and ruin a loaf. Baker's percentages only work with weight, so a kitchen scale is essential here.
Written by Nicolas Martin, who bakes his own sourdough and built these tools for his own kitchen. Last updated July 2026 · How we keep our tools accurate →