Sourdough Hydration Calculator
Calculate the true hydration of a dough once the water and flour in the starter are counted.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
About this calculator
Starter is half flour and half water at 100% hydration, so adding it changes both sides of the hydration calculation. The true hydration is always slightly lower than the water you poured in.
Worked example
calculated with the default values below
Flour added 500 g · Water added 375 g · Starter 100 g · Starter hydration 100 % True hydration 77.3 % · Total flour 550.0 g · Total water 425.0 g · Total dough weight 975 g
Method and assumptions
H = (w + S − S÷(1+p÷100)) ÷ (F + S÷(1+p÷100)) × 100 Starter flour = starter mass ÷ (1 + starter hydration); starter water is the remainder. True hydration = total water ÷ total flour × 100; it is undefined when total flour is zero. Starter is half flour and half water at 100% hydration, so adding it changes both sides of the hydration calculation. The true hydration is always slightly lower than the water you poured in. The references explain definitions and methods; any extra preset must be checked against the assumptions on this page.
Data sources
The references explain definitions and methods; any extra preset must be checked against the assumptions on this page.
Disclaimer
These calculators give general cooking guidance. Ingredient density, oven calibration, altitude and equipment all vary, and safe minimum internal temperatures always take precedence over timings. Follow the food-safety advice issued by your national authority.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
H = (w + S − S÷(1+p÷100)) ÷ (F + S÷(1+p÷100)) × 100
- F
- Flour added (g)
- w
- Water added (g)
- S
- Starter (g)
- p
- Starter hydration (%)
Starter flour = starter mass ÷ (1 + starter hydration); starter water is the remainder. True hydration = total water ÷ total flour × 100; it is undefined when total flour is zero.
Frequently asked questions
Does starter hydration affect the result?
Yes. The starter’s flour and water are included according to its entered hydration. If total flour is zero, true hydration is undefined and is left blank.
Which inputs and limits apply to Sourdough Hydration Calculator?
Use the units shown beside each field. These are form limits, not recommended settings. Flour added: 0–100,000 g; Water added: 0–100,000 g; Starter: 0–100,000 g; Starter hydration: 50–150 % H = (w + S − S÷(1+p÷100)) ÷ (F + S÷(1+p÷100)) × 100 Starter flour = starter mass ÷ (1 + starter hydration); starter water is the remainder. True hydration = total water ÷ total flour × 100; it is undefined when total flour is zero. Starter is half flour and half water at 100% hydration, so adding it changes both sides of the hydration calculation. The true hydration is always slightly lower than the water you poured in. The references explain definitions and methods; any extra preset must be checked against the assumptions on this page.
What is a complete worked example for Flour added = 500 g; Water added = 375 g?
Inputs: Flour added = 500 g; Water added = 375 g; Starter = 100 g; Starter hydration = 100 %. Calculation: H = (w + S − S÷(1+p÷100)) ÷ (F + S÷(1+p÷100)) × 100. Results: True hydration = 77.3 %; Total flour = 550.0 g; Total water = 425.0 g; Total dough weight = 975 g.