Baker's Percentage Calculator

Why this disagrees with other calculators

Set prefermented flour to 20% and levain hydration to 100%, and this tool will tell you to add less water than most calculators do. It isn’t a rounding difference — the two are answering different questions.

A levain is flour and water. At 100% hydration, 200 g of levain is 100 g of flour and 100 g of water. Those aren’t a separate ingredient sitting outside the formula; they’re part of the dough, and if you don’t count them, the loaf you actually bake is wetter than the number you asked for.

This calculator expresses everything against total flour, including the flour in the levain — the convention used in professional formulas, and the one where “75% hydration” describes the dough that goes in the oven rather than an intermediate step nobody eats.

At 20% prefermented flour the gap is about three points of true hydration. At 40%, it’s more than six. That’s the difference between a dough you can shape and one that spreads.

The arithmetic

Nothing here is hidden. With F as total flour, h as hydration, s as salt, pf as the fraction of flour that’s prefermented, and lh as levain hydration:

levain flour = F × pf
levain water = levain flour × lh
levain       = levain flour + levain water

add flour    = F − levain flour
add water    = (F × h) − levain water
salt         = F × s

total dough  = F × (1 + h + s)

Working backwards from a dough weight is the same equation rearranged: F = dough ÷ (1 + h + s). That’s the direction most bakers actually need — you size a batch to the banneton you own, not the other way round — and it’s the mode most calculators don’t offer.

A note on salt

Salt is given as a percentage of total flour, which is how formulas are written, not as a percentage of dough. 2% is the usual working range; below about 1.5% the loaf tastes flat and ferments faster than you expect, and above about 2.5% fermentation drags noticeably.