Converting a Sourdough Recipe to Different Loaf Sizes

Most sourdough recipes are written for one specific loaf size. A 900g boule for a 5-quart Dutch oven. A 1kg batard for a standard banneton. A modest 750g loaf because that’s what the recipe developer bakes. Which is fine — until your vessel is a different size, you’re baking for a crowd, or you’ve fallen in love with a recipe that just doesn’t fit what you need.

Converting a sourdough recipe to a different loaf size is one of those skills that feels complicated until you understand the underlying logic, and then it becomes second nature. Once you’re working in baker’s percentages, you can hit any target dough weight you want without touching a single ratio. Here’s how it works.

Why Sourdough Scales Cleanly (When You Do It Right)

Sourdough recipes are fundamentally ratio-based. The percentages of water, salt, and starter are all calculated against the flour weight. Change the flour weight and everything else scales with it proportionally. That’s the whole point of baker’s percentages — they describe a dough, not a specific batch size.

This means a recipe calling for 500g flour, 375g water, 100g starter, and 10g salt (75% hydration, 20% starter, 2% salt) is really just saying: make a 75/20/2 dough. You can make 800g of that dough or 1,600g of that dough and it will behave identically — same hydration, same fermentation rate, same crumb structure. Only the math changes.

The tricky part is working backward from your target loaf weight to the flour weight you need.

Step One: Know Your Target Dough Weight

Before you can convert anything, you need to know how much dough your target loaf requires. This varies by vessel and loaf style:

Standard 5-quart round Dutch oven: typically suits 850g–1,000g of dough
Oval Dutch oven or oblong banneton: 900g–1,100g depending on length
Standard 9x5 inch loaf pan: 800g–950g for a well-domed sandwich loaf
Small 8x4 inch loaf pan: 600g–750g
Large oval banneton (10-inch): 1,000g–1,200g
Mini boules or individual rolls: 200g–350g each

These are starting ranges, not hard rules. If you’ve baked in a vessel before and your loaf looked a little flat or a little cramped, adjust up or down by 100–150g from whatever you used last time.

One useful rule of thumb: finished baked loaves lose roughly 10–15% of their dough weight during baking as steam evaporates. So if you want a finished loaf that weighs 800g, you need roughly 900–950g of dough going in.

Step Two: Back-Calculate Your Flour Weight

This is where baker’s percentages earn their keep. Since all ingredients are expressed as a percentage of flour, you can calculate the required flour weight from your target dough weight using a single formula:

Flour weight = Target dough weight ÷ (sum of all percentages / 100)

For a recipe with 75% hydration, 20% starter, and 2% salt, your percentages add up to 197% (100% flour + 75% water + 20% starter + 2% salt = 197%).

If your target dough weight is 950g:

Flour = 950 ÷ 1.97 = 482g

Then scale every other ingredient from that flour weight:

Water: 482 × 0.75 = 362g
Starter: 482 × 0.20 = 96g
Salt: 482 × 0.02 = 10g
Total dough: 950g ✓

That’s the whole conversion. The formula holds for any recipe and any target dough weight.

Step Three: Round Sensibly

Real-world baking doesn’t require gram-perfect precision on every ingredient. Once you’ve calculated your scaled amounts, round to the nearest 5g for flour and water, and to the nearest gram for salt. Starter can usually be rounded to the nearest 5g as well without meaningful impact on fermentation.

The one place not to round aggressively is salt. Salt affects both flavor and fermentation rate, and because the amounts are small to begin with, rounding 9.6g to 10g is fine, but rounding to 8g or 12g is not. Keep salt within about 0.5g of your calculated amount.

When You’re Converting Across Vessel Types

Different vessels don’t just need different dough weights — they can call for different shaping and hydration ranges. A few things to keep in mind:

Loaf pans vs. free-form boules: Pan loaves are more forgiving at higher hydrations because the pan provides structure the dough doesn’t have to provide itself. A 78% hydration dough that spreads sideways in a free-form bake holds its shape fine in a pan. If you’re converting a free-form recipe to a pan loaf, you can often push hydration up 3–5%. Conversely, if you’re taking a pan recipe free-form, you may want to drop hydration slightly.

Round Dutch ovens vs. oval bannetons: Mostly a shaping consideration, not a formula one. The dough weight ranges overlap significantly. What changes is how you pre-shape and final-shape the dough, not the ratios.

Mini loaves and rolls: These bake faster and cool faster than full-size loaves. If you’re converting a recipe to individual rolls (say, 100g each), expect a significantly shorter bake time — 20–25 minutes at high heat rather than 45–55. Keep a close eye and test doneness by internal temperature (210°F / 99°C) rather than color alone.

Fermentation Timing Stays (Mostly) the Same

Here’s a reassuring one: when you convert a sourdough recipe to a different loaf size, your fermentation timing usually doesn’t need to change. Bulk fermentation and final proof are driven by dough temperature and inoculation rate — neither of which changes when you scale the batch up or down.

A 950g batch at the same dough temperature with the same starter percentage will bulk in the same window as a 700g batch. You’re looking for the same fermentation cues: 50–75% volume rise, domed surface, visible bubble structure, and dough that feels airy and passes the poke test. The clock doesn’t really change just because the batch size did.

The exception is if you’re significantly changing batch size — say, from one small loaf to four large ones. In that case, thermal mass effects can come into play (larger dough masses hold heat longer), and baking logistics mean your later loaves will continue proofing during earlier bakes. The Bulk Fermentation Calculator is useful here — plug in your actual dough temperature and starter percentage to get a grounded time estimate for your specific conditions.

Adjusting Starter With Loaf Size Changes

If you’re converting to a significantly different loaf size, your starter requirement changes proportionally. This sometimes means adjusting your feeding to ensure you have enough active starter on bake day without wasteful excess.

For example, if you normally bake one 900g loaf using 100g starter, and you’re converting to three 700g loaves, you now need roughly 280g of active starter. That may require a larger feed the night before, or an additional feeding cycle depending on your starter’s typical rise timeline.

The Starter Feeding Calculator handles this well — input how much starter you need at peak and it works backward to tell you what feed ratio and timing to use. Worth running before bake day any time you’re changing batch sizes meaningfully.

Skip the Manual Math

The formula above is straightforward, but doing it by hand for every bake — especially when you’re adjusting multiple variables at once — gets tedious fast. The Recipe Scaler at CrumbDesk automates the whole process. Enter your original recipe and your target loaf size (or target dough weight), and it outputs every ingredient scaled precisely with baker’s percentages intact.

It handles non-round conversions cleanly — converting a single 1kg loaf recipe to two 750g loaves, or scaling a recipe designed for a 9x5 pan to fit an 8x4 — without rounding errors accumulating across ingredients. Particularly useful when you’re working with recipes that have multiple flour types, preferments, or add-ins that all need to scale together.

FAQ

How do I know if my Dutch oven is the right size for a recipe? A standard 5-quart (4.7L) round Dutch oven handles dough in the 850g–1,050g range well. For smaller amounts the loaf can spread and come out squat; for larger amounts it may be cramped and lack oven spring. If your oven runs smaller (3.5–4 quart), target 700–850g of dough.

Do I need to change bake temperature when converting to a smaller loaf? Temperature can stay the same; time is what changes. Smaller loaves bake faster and hit internal temperature sooner. Start checking doneness 5–10 minutes earlier than the original recipe suggests, and rely on internal temperature (210°F / 99°C) over bake time.

Can I use this method for enriched sourdough recipes — brioche, sandwich loaves with butter and eggs? Yes, baker’s percentages work the same way for enriched doughs. The add-ins (butter, eggs, milk) are each expressed as a percentage of flour and scale linearly. The main difference is that enriched doughs typically don’t follow the same fermentation rate rules as lean doughs, so timing may need adjustment separately.

What if I want to convert a recipe that doesn’t use baker’s percentages? First, convert it. Divide every ingredient by the flour weight and express as a percentage. Once you have the percentages, the scaling formula works normally. Most well-documented sourdough recipes either list baker’s percentages directly or give enough detail that you can calculate them.

My loaf keeps coming out too flat after I scaled up. What’s happening? A few possibilities: your dough weight may be too much for your vessel, leading to a loaf that spreads sideways rather than rising up; your bulk fermentation may have gone slightly long as a result of thermal mass in a larger batch; or shaping tension may have been lost trying to handle more dough than you’re used to. Try scaling back 100–150g and see if the shape improves.

Once you’ve run through a conversion or two, the logic becomes automatic. Baker’s percentages exist precisely so recipes aren’t locked to a specific batch size — they’re just descriptions of a dough, waiting for you to tell them how much of it you need.

Ready to convert your recipe? Use the Recipe Scaler at CrumbDesk →