Sourdough Bread Calculator

What Baker's Math Actually Means for Your Bread

Baker's math (also called baker's percentages) is the standard language professional bakers use worldwide. The idea is straightforward: flour is always 100%, and every other ingredient is expressed as a percentage of the total flour weight. If you have 500 grams of flour and your recipe calls for 67% water, that means 335 grams of water. Simple arithmetic, but it eliminates the guesswork when you want to scale a recipe up for a dinner party or down for a single weeknight loaf.

This calculator builds on that system. You set your flour weight per loaf, choose how many loaves you need, and adjust hydration and starter percentages using the sliders. Salt defaults to 2% because that is the sweet spot most experienced bakers land on after years of experimenting, but you can nudge it anywhere between 1% and 4% if your palate or dietary needs call for it.

Understanding Hydration and Why It Matters

Hydration is the single variable that changes everything about your sourdough: how it handles on the bench, how it rises in the oven, how the crumb looks when you slice it, and even how it tastes. A 55% hydration dough will feel like modelling clay in your hands. A 85% hydration dough will stick to every surface it touches and demand serious bench-scraper skills. Most home bakers find their comfort zone somewhere between 65% and 72%.

Low Hydration (50% to 59%)

Stiff doughs in this range are easy to shape and hold their structure well during proofing. The crumb will be tight and dense, which makes the bread ideal for sandwich loaves where you need slices that won't fall apart. Bagels typically sit around 55% hydration. If you are just starting out with sourdough and find sticky dough frustrating, working in this range lets you build confidence before gradually increasing water content.

Medium Hydration (60% to 75%)

This is where most everyday sourdough lives. At 65% you get a dough that is manageable by hand, with a crumb that has a nice mix of small and medium air pockets. Push it to 72% and you will notice the dough getting tackier, the crust getting crispier, and the crumb opening up with larger, more irregular holes. If you are baking your first sourdough loaf, 67% is the recommended starting point. It is forgiving enough to handle shaping mistakes while still producing bread with a satisfying chew and a golden, crackly crust.

High Hydration (76% to 90%)

High-hydration doughs reward patience and technique. The bread produced at these levels has that coveted open crumb with large, glossy holes, a thin shattering crust, and a custardy interior. Ciabatta and focaccia typically range from 78% to 85%. Working with these doughs usually requires a stand mixer or extensive stretch-and-fold sessions during bulk fermentation. The dough will be very slack and sticky, so dust your bench with rice flour rather than bread flour for shaping, as rice flour won't get absorbed into the dough.

How Starter Percentage Affects Fermentation

Your sourdough starter is a living colony of wild yeast and lactic acid bacteria. The percentage of starter you add to your dough controls the speed of fermentation. More starter means a faster rise because you are introducing a larger population of microorganisms right from the start. Less starter means a slower, longer fermentation that develops more complex flavours.

Most recipes call for somewhere between 15% and 25% starter relative to flour weight. At 20%, a typical room-temperature bulk fermentation takes around four to five hours, depending on how warm your kitchen is. Drop to 10% and you might be looking at eight hours or overnight on the counter. Go up to 40% and the dough can be ready in under three hours, though the flavour will be milder since the bacteria haven't had as much time to produce organic acids.

Temperature and Starter Timing

Kitchen temperature is the hidden variable that trips up many home bakers. Fermentation roughly doubles in speed with every 8 to 10 degree Celsius increase. In a warm summer kitchen at 28 degrees, 15% starter might ferment as quickly as 25% would in a 20-degree kitchen. The general guideline: if your kitchen is above 24 degrees Celsius (75 degrees Fahrenheit), use less starter, around 10% to 15%. If your kitchen sits below 20 degrees Celsius (68 degrees Fahrenheit), bump the starter up to 25% or even 30% to keep fermentation on schedule.

Effective Hydration Explained

This calculator shows you something most basic sourdough calculators miss: the effective hydration of your dough. Your sourdough starter (assuming it is 100% hydration, which means equal parts flour and water by weight) contains both flour and water. When you add 100 grams of starter to your dough, you are actually adding 50 grams of flour and 50 grams of water. The effective hydration formula accounts for this:

Effective Hydration = (Total Water + Starter Water) / (Total Flour + Starter Flour) x 100

So if you set flour to 500 grams, water to 67% (335 grams), and starter to 20% (100 grams), the raw hydration is 67% but the effective hydration is about 71%. That four-point difference matters when you are dialling in your preferred dough consistency.

Salt in Sourdough Baking

Salt does three things in bread: it strengthens the gluten network, controls fermentation speed, and adds flavour. Without salt, your dough will be slack, ferment too fast, and taste flat. The standard is 2% of flour weight. Some bakers go up to 2.5% for a more pronounced flavour, particularly in rye-heavy loaves. Going below 1.5% makes it harder to build good gluten structure and the bread will taste noticeably bland.

Kosher salt and fine sea salt are preferred because they dissolve easily and distribute evenly through the dough. Avoid iodised table salt since the iodine can give bread a faint metallic taste. If you are using coarse salt, dissolve it in a tablespoon of warm water before adding it to the dough to make sure it distributes uniformly.

Flour Selection for Different Outcomes

The type of flour you choose is as important as the ratios in your recipe. Strong bread flour with 12% to 14% protein gives you a chewy crumb with good oven spring. All-purpose flour (around 10% to 12% protein) produces a softer, more tender loaf. Whole wheat flour absorbs more water than white flour, so if you are substituting, you will want to increase hydration by 3% to 5% to compensate.

Rye flour is popular in sourdough baking because it ferments vigorously, but it has very little gluten, so most bakers blend it at 10% to 20% with bread flour. Spelt flour produces a wonderfully nutty flavour but has fragile gluten, meaning you should handle the dough gently and keep hydration on the lower end.

Scaling Recipes for Multiple Loaves

One of the practical advantages of this calculator is the ability to scale recipes by loaf count. If you normally bake a single 500-gram-flour loaf and want to make four for a weekend farmers market, just change the loaf count to four. The calculator multiplies all ingredients proportionally. The only thing to watch out for when scaling up is that larger batches of dough ferment slightly faster than small batches because the dough mass retains heat more effectively. You may need to reduce your starter percentage by a few points or shorten the bulk fermentation time when scaling from one loaf to six or more.

Practical Tips from Experienced Bakers

• Autolyse first: Mix flour and water, let it rest for 30 to 60 minutes before adding starter and salt. This kick-starts gluten development without any kneading.
• Use a kitchen scale: Volume measurements (cups) are unreliable for bread baking. A gram scale accurate to 1 gram is the most important piece of equipment you can own.
• Cold retard overnight: After shaping, put your dough in the refrigerator for 12 to 18 hours. Cold fermentation develops deeper, more complex sour flavours and makes scoring much easier because the cold dough holds its shape under the blade.
• Steam the oven: Moisture in the first 15 minutes of baking keeps the crust flexible so the bread can expand fully. Use a Dutch oven with the lid on, or throw a handful of ice cubes into a preheated cast-iron pan on the lowest rack.
• Wait before slicing: The interior of your bread is still setting for at least an hour after it comes out of the oven. Cutting too early releases steam and can make the crumb gummy.

Common Sourdough Troubleshooting

Flat loaves usually point to one of three issues: underfermented dough (not enough bulk fermentation time), weak starter (feed it twice a day for three days to build strength), or poor shaping technique (the surface tension wasn't tight enough). Dense crumb with small holes typically means the dough was underhydrated or overworked during shaping. An overly sour taste comes from extended fermentation, especially at warm temperatures. Pull the dough earlier or use the refrigerator to slow things down.

If your crust is too thick and hard, you likely baked with steam for too long or at too high a temperature. Remove the Dutch oven lid after 20 minutes and drop the temperature by 10 degrees for the remaining bake. If the bottom burns before the top is done, place your baking vessel on a sheet pan or lower the rack position.