ABC Tools

Baker's Percentage & Dough Calculator, Explained

After reading this you will be able to write a bread formula in baker's percentages, scale it to any batch size, and account for the flour and water hidden inside your starter so your true hydration is the number you actually meant.

What baker's percentages are

A baker's percentage is a weight expressed as a fraction of the total flour, with flour fixed at 100%. This is not a normal percentage. The numbers in a formula do not add up to 100. Instead, every ingredient is measured against the flour, and the flour is measured against itself.

Take a plain loaf: 1000 g flour, 700 g water, 20 g salt. Water is 700 / 1000 = 70%. Salt is 20 / 1000 = 2%. Flour is 100% by definition. Written as a formula it reads flour 100%, water 70%, salt 2%. That single line describes the recipe at any size. Want a small test bake with 300 g flour? Multiply each percentage by 3 g: 210 g water, 6 g salt. The ratios never change, only the base flour weight.

This is why professional bakers speak in percentages and never in cups. A percentage survives scaling from a single loaf to a 50 kg mixer without any arithmetic drift, and it lets you compare two recipes at a glance. A 65% dough is stiffer than a 78% dough regardless of batch size.

When to use it, and when not

Reach for baker's percentages whenever you are developing a recipe, scaling a known recipe up or down, or comparing formulas. If you have ever tripled a recipe and ended up with dough that felt wrong, the cause was almost always rounding cups. Weights in grams fix that.

Percentages are less useful for the finishing steps that do not scale with flour: the dusting of semolina on the peel, the steam in the oven, the exact number of folds. Those depend on your equipment and technique, not on batch size. Keep them as notes, not as percentages.

Everything here assumes weight, not volume. A cup of flour can vary by 20% depending on how you scoop it. If you are serious about repeatable bread, a kitchen scale that reads to 1 g is the single change that matters most.

The math, and the starter gotcha

Start from the flour you weigh out, call it F. Every other core ingredient is a percentage p of that flour:

W_{\text{ingredient}} = F \times \frac{p}{100}

Here W_{\text{ingredient}} is the weight in grams, F is the base flour in grams, and p is that ingredient's baker's percentage. Water at 70% of 1000 g gives 700 g. Salt at 2% gives 20 g. Simple.

The starter breaks the simplicity, and this is where most home bakers get their hydration wrong. A levain or sourdough starter is itself a mix of flour and water. When you add a 20% starter, you are not adding 20% of some neutral ingredient. You are adding more flour and more water on top of what you already counted.

Let the starter percentage be s and its own hydration be h_s (as a percent). The starter weight is S = F \times s / 100. Inside that starter, flour and water split according to its hydration:

F_{\text{starter}} = \frac{S}{1 + h_s/100}, \qquad W_{\text{starter}} = S - F_{\text{starter}}

The logic: if hydration is 100%, the starter is equal parts flour and water, so a 200 g starter holds 100 g flour and 100 g water. Plug h_s = 100 into the formula and the denominator is 2, giving exactly half. A stiff 50% starter of 200 g holds 200 / 1.5 = 133.3 g flour and 66.7 g water.

Now the true totals, the numbers that decide how your dough handles:

F_{\text{true}} = F + F_{\text{starter}}, \qquad \text{Hydration}_{\text{true}} = \frac{W + W_{\text{starter}}}{F_{\text{true}}} \times 100

where W is the plain water you weighed out. Because the starter adds both flour and water, the true hydration is almost never the number you typed. It shifts toward the starter's hydration.

If you type 70% hydration and add a 100% starter, your dough is wetter than 70%. Bakers who ignore this wonder why their "70% dough" is soupy. The calculator reports the true hydration so you can adjust the plain water down if you want to hit a target.

A worked example matching the demo

1000 g flour, 70% hydration, 20% starter at 100%

These are the demo button values: work from flour, 1000 g base flour, 70% hydration, 2% salt, 20% starter, 100% starter hydration.

  1. Plain water: 1000 × 0.70 = 700 g.
  2. Salt: 1000 × 0.02 = 20 g.
  3. Starter weight: 1000 × 0.20 = 200 g.
  4. Flour inside the starter: 200 / (1 + 1.00) = 100 g. Water inside: 200 - 100 = 100 g.
  5. True total flour: 1000 + 100 = 1100 g.
  6. True total water: 700 + 100 = 800 g.
  7. True hydration: 800 / 1100 = 72.7%.

You typed 70% but the dough is really at 72.7%. That 2.7 point jump is the starter's water. If you wanted a true 70%, you would drop the plain water to about 670 g: (670 + 100) / 1100 = 70.0%.

The total dough weight is 1000 + 700 + 20 + 200 = 1920 g. Split into 2 loaves, that is 960 g each before baking loss.

How the starter shifts hydration

The effect grows with both how much starter you add and how wet that starter is. The chart below holds plain hydration at 70% and 1000 g base flour, then varies the starter percentage for two starter hydrations.

A liquid (100%) starter pushes true hydration up sharply as you add more of it. A stiff (50%) starter barely moves it, because its water content is low.

Read the 20% column: a 100% starter lands you at 72.7% (the demo), while a 50% starter of the same size lands at only 70.3%. Same amount of starter, very different dough, because the stiff starter carries far less water.

With 1000 g base flour and 70% plain hydration: a 20% starter at 100% hydration gives 1100 g true flour and 72.7% true hydration. Raising the starter to 40% gives 1200 g true flour and 75.5% true hydration. Dropping starter hydration to 50% at 20% starter gives 1133 g true flour and 70.3% true hydration.

Reading the results

The calculator gives you several numbers. Keep them straight:

Flour to weigh out
The plain flour you scoop onto the scale, excluding whatever is locked in the starter. In the demo this is 1000 g.
True total flour
All flour in the dough, including the starter's share. 1100 g in the demo. Use this only for understanding hydration, not for weighing.
True hydration
The water-to-flour ratio the dough actually experiences. This governs stickiness, spread, and crumb, so it is the number to trust when a recipe feels off.
Per-loaf split
Total dough divided by the number of loaves. Divide before shaping, not after, so every loaf is the same size.

The scaling table (half, single, double) exists so you can commit to a batch size without redoing arithmetic. Halving the demo gives 500 g flour, 350 g water, 10 g salt, 100 g starter. The ratios are identical, so the bread is identical.

Common mistakes

The first mistake is counting the starter's flour twice or not at all. If a recipe says "1000 g flour plus 200 g starter," decide whether that 1000 g already includes the starter's flour. This calculator treats your base flour as the plain flour only, then adds the starter's flour on top.

The second is chasing someone else's hydration number without knowing their starter. A blog recipe at "75% hydration" with a stiff starter is a different dough from your version with a liquid levain, even at the same typed percentage. Compare true hydration, not typed hydration.

The third is salt drift when scaling by volume. Salt sits in a narrow band, 1.8% to 2.2% of flour. At 2% you have 20 g per kilo of flour. Go to 2.5% and the dough tastes salty and ferments sluggishly; drop to 1% and it tastes flat and proofs too fast. Weigh salt to the gram.

The fourth is forgetting that baking drives off water. A 960 g raw loaf comes out of the oven near 860 g after losing 10% to 12% as steam. Size your dough pieces for the raw weight, not the finished weight.

Related tools

If your kitchen projects go beyond bread, a few neighbours may help. The Coffee Brew Ratio & Extraction Calculator uses the same ratio thinking, dose against water, that baker's percentages use. The Brewing ABV & Recipe Calculator handles fermentation math for beer and cider. For precise temperature control on meat and eggs, the Sous Vide Time & Safety Calculator gives come-up time and pasteurization holds.

Frequently asked questions

Why does my true hydration come out higher than what I typed?

Because your starter carries water. A 100% starter is half water by weight, so adding it raises the total water faster than it raises the total flour. In the demo, 70% typed becomes 72.7% true. To hit a true target, lower the plain water until the true figure matches.

What hydration should I use?

Most everyday breads sit between 65% and 75%. Below 65% the dough is stiff and easy to shape but tight in crumb. Above 75% it spreads and needs skilled handling but gives an open, holey interior. Start at 70% and adjust by 2 to 3 points at a time.

How do I convert a stiff starter to a liquid one in the formula?

Change the starter hydration field, not the starter percentage. A 50% starter and a 100% starter at the same 20% add the same total starter weight but different amounts of water: 66.7 g versus 100 g in a 200 g starter. The calculator recomputes the true hydration for you.

Do the percentages have to add up to anything?

No. Flour is 100% and everything else is measured against it, so a typical formula sums to well over 100% (roughly 192% in the demo). That is expected. The sum is not a target; it is just the total dough weight divided by the flour weight, times 100.

Can I add seeds, oil, or sugar?

Yes, as extra ingredients, each written as a percent of the base flour. Oil at 3% of 1000 g is 30 g. Note that fats and sugars change how the dough handles and browns, but they do not count as water, so they do not enter the hydration figure.

Try it yourself in the tool

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