🥖 Sourdough Hydration & Baker’s Percentage Calculator
Calculate artisan sourdough dough hydration percentages, main flour, water, 100% hydration starter/levain, and salt weights with baker’s math.
Assumes a 100% hydration (liquid) starter — equal parts flour and water by weight.
What Sourdough Hydration & Baker’s Percentage Calculator Does
This calculator turns four numbers — total recipe flour, target hydration, sourdough starter weight, and salt percentage — into the four things you actually weigh out: main flour, water to add, starter, and salt, plus the total batch weight. It works in baker’s percentage, where every ingredient is expressed as a share of total flour weight, so "75% hydration" means 75g of water for every 100g of flour in the whole dough, starter included.
Because the starter is assumed to be equal parts flour and water by weight (a 100%-hydration starter), the tool can solve for exactly how much flour and water to add on top of it. As long as the starter’s own water and flour fit inside what the target hydration already calls for, the resulting true hydration lands exactly on the target you typed — it isn’t rounded to match, it comes out equal by construction. That stops being true once the starter is large enough that the main-dough water would have to go negative to hit the target: the water card floors at 0g, and the true hydration you get is higher than the one you asked for. That threshold, and what it looks like when you cross it, is worked out below.
The total batch weight shown is the sum of the four ingredient cards exactly as rounded on screen, not a separately rounded raw total, so the headline weight and the ingredient list underneath it never disagree with each other by a few tenths of a gram.
How to Use Sourdough Hydration & Baker’s Percentage Calculator
- Enter total recipe flour weight in grams and target hydration percentage (e.g. 75%)
- Input sourdough starter weight and salt percentage (typically 2%)
- Review exact weight measurements for main flour, water, starter, and sea salt
Formula Used by Sourdough Hydration & Baker’s Percentage Calculator
Total water from target hydration
Total Water (g) = Total Flour (g) × Target Hydration (%) ÷ 100
- Total Flour
- Grams entered in "Total Recipe Flour" — includes the flour inside the starter
- Target Hydration
- The percentage you enter, as water weight relative to total flour weight
- Total Water
- Combined water across the whole dough, main dough plus starter
Worked example
Total flour 500g, target hydration 75%.
- Total Water = 500 × 75 ÷ 100 = 375
Result: 375g of water across the entire dough, before any of it is assigned to the starter.
Splitting a 100%-hydration starter
Starter Flour (g) = Starter Water (g) = Starter Weight (g) ÷ 2
- Starter Weight
- Grams entered in "Sourdough Starter / Levain"
Worked example
Starter weight 100g.
- Starter Flour = 100 ÷ 2 = 50
- Starter Water = 100 ÷ 2 = 50
Result: 50g of the total flour and 50g of the total water are already sitting in the starter.
Main flour and water to add
Main Flour = max(0, Total Flour − Starter Flour); Main Water = max(0, Total Water − Starter Water)
- max(0, …)
- The subtraction is floored at zero — it can never show a negative weight
Worked example
Continuing the 500g flour / 75% hydration / 100g starter example above.
- Main Flour = max(0, 500 − 50) = 450
- Main Water = max(0, 375 − 50) = 325
Result: 450g flour and 325g water to add, on top of the 100g starter.
Salt weight
Salt (g) = Total Flour (g) × Salt % ÷ 100
- Salt %
- Percentage entered, relative to total flour weight
Worked example
Total flour 500g, salt percentage 2.0%.
- Salt = 500 × 2.0 ÷ 100 = 10
Result: 10.0g of salt.
True hydration, and where it parts ways with the target
True Hydration (%) = (Main Water + Starter Water) ÷ (Main Flour + Starter Flour) × 100
- True Hydration
- What the dough is actually mixed to, once the starter is counted
Worked example
Total flour 400g, target hydration 75%, starter 700g — a starter heavier than the total flour itself.
- Starter Flour = Starter Water = 700 ÷ 2 = 350
- Total Water target = 400 × 75 ÷ 100 = 300
- Main Water = max(0, 300 − 350) = 0 (would have been −50, floored)
- Main Flour = max(0, 400 − 350) = 50
- True Hydration = (0 + 350) ÷ (50 + 350) × 100 = 87.5
Result: The water-to-add card reads 0g and the true hydration comes out to 87.5%, 12.5 points above the 75% typed in — because the starter alone already carries more water than the whole target recipe called for. The divergence starts exactly when starter weight exceeds 2 × Total Flour × Target Hydration ÷ 100 (here, 2 × 400 × 0.75 = 600g; 700g crosses it).
Starter Size at Which True Hydration Stops Matching Your Target
Below this starter-to-flour ratio, true hydration equals your target exactly. Above it, main-dough water floors at 0g and true hydration reads higher than the target you entered. Ratio = 2 × Target Hydration ÷ 100.
| Target hydration | Starter ÷ total flour ratio | Starter weight as % of total flour |
|---|---|---|
| 60% | 1.20 | 120% |
| 65% | 1.30 | 130% |
| 70% | 1.40 | 140% |
| 75% | 1.50 | 150% |
| 80% | 1.60 | 160% |
| 85% | 1.70 | 170% |
| 90% | 1.80 | 180% |
Same Target Hydration, Two Starter Builds
Both rows target 75% hydration. The second uses a starter heavier than the total flour, which is enough to push true hydration above target.
| Scenario | Total flour | Starter | Main flour (shown) | Water to add (shown) | True hydration |
|---|---|---|---|---|---|
| Typical build | 500g | 100g | 450g | 325g | 75.0% |
| Starter over threshold | 400g | 700g | 50g | 0g | 87.5% |
What 100g of Starter Actually Contains, by Starter Hydration
This tool always assumes a 100%-hydration (liquid) starter — a flat 50g flour / 50g water per 100g of starter, regardless of what you actually feed. A stiffer starter contains more flour and less water than that.
| Starter hydration | Actual flour in 100g starter | Actual water in 100g starter | This tool assumes |
|---|---|---|---|
| 100% (liquid — matches this tool) | 50.0g | 50.0g | 50.0g / 50.0g — exact match |
| 75% | 57.1g | 42.9g | 50.0g / 50.0g — overstates water by 7.1g |
| 60% | 62.5g | 37.5g | 50.0g / 50.0g — overstates water by 12.5g |
| 50% (stiff, e.g. lievito madre) | 66.7g | 33.3g | 50.0g / 50.0g — overstates water by 16.7g |
How to Read Your Result
Why true hydration almost always equals your target
Add main flour back to starter flour and you get total flour again; add main water back to starter water and you get total water again — as long as neither subtraction below them went negative. So the true-hydration ratio is guaranteed to equal the target ratio you typed, not because the tool rounds it to match, but because the two subtractions cancel out algebraically. This holds for any starter size that fits inside the target recipe’s own flour and water budget.
When the starter takes over the dough
Once a starter is large enough to exceed that budget — see the ratio table above — the water-to-add card can read 0g, meaning literally none of the total water needs to be mixed in separately because the starter already supplies more than the target called for. When you see a 0g water or 0g flour card, that is the tool telling you the levain build itself is bigger than the final dough’s own target allows, not a recipe you can actually mix as typed. The fix is to shrink the starter or raise the target hydration to match it, not to add negative water.
The total always matches what is on screen
The total batch weight is calculated by summing the four ingredient cards after they are rounded for display, not by rounding a separately computed raw total. That means the big number at the top of the results is always exactly the sum of the flour, water, starter and salt figures printed underneath it — it cannot drift a tenth of a gram away from what you would get adding the four cards yourself.
A liquid starter is not the only kind
Plenty of sourdough methods use a stiff starter or leaven instead of a liquid one — an Italian lievito madre is typically fed at 50-60% hydration, not 100%. This tool has no field for starter hydration; it always splits whatever weight you enter 50/50. Per the table above, a 60%-hydration starter actually contains 62.5g flour and 37.5g water per 100g, not the 50g/50g this tool assumes, so plugging a stiff starter’s full weight in here overstates the water it contributes and your finished dough will mix up drier than the cards suggest.
Limitations & Accuracy Notes
- Assumes a 100%-hydration (liquid) starter — equal parts flour and water by weight, as stated on the page itself. A stiff or low-hydration starter (commonly 50-60%) is not supported; see the interpretation above for how far off the flour/water split runs at 100g.
- One flour figure only. There is no breakdown across multiple flours — bread flour, whole wheat, rye — each of which absorbs water differently, and no per-flour baker’s percentage output.
- No scaling to a target final dough weight, pan size, or number of loaves. It works forward from flour, hydration, starter, and salt to a resulting batch weight, not backward from "I need 900g of dough."
- No bulk fermentation or proofing time guidance. A higher-hydration dough ferments differently at a given temperature; this tool has no time, temperature, or fermentation model at all.
- Negative inputs are floored at zero, but an oversized starter is allowed to silently push main water or main flour to 0g rather than being flagged as an impossible recipe. The true-hydration reading rising above your target is the only on-page signal that this happened.
- Salt is shown only in grams as a percentage of total flour weight — no teaspoon/tablespoon conversion, and no distinction between fine sea salt, kosher salt, or table salt, which pack to different weights at the same volume.
Frequently Asked Questions
What is Baker’s Hydration percentage?
How does starter hydration affect the recipe?
How is hydration calculated?
Does the starter count toward hydration?
What hydration should I use?
Why is my high-hydration dough not holding its shape?
Does hydration change the bake?
Is my recipe stored?
References & Further Reading
- Wikipedia — Baker percentage — General reference for the baker’s-percentage notation this tool implements (all ingredient weights expressed relative to total flour weight = 100%). No government or standards body defines this baking convention.