Sourdough Hydration Calculator ·
Keep the totals fixed
Suppose your formula uses 500 g added flour, 350 g added water and 100 g starter at 100% hydration. The starter contributes 50 g flour and 50 g water, so the dough contains 550 g total flour and 400 g total water: 72.73% hydration. If you change only the starter hydration, those totals change unless you compensate elsewhere.
Convert the starter composition
Change the 100 g starter to 60% hydration. A 100 g starter at 60% contains 62.5 g flour and 37.5 g water. Compared with the original starter, that is 12.5 g more flour and 12.5 g less water inside the same 100 g starter weight.
Adjust the added flour and water
To preserve 550 g total flour, reduce the added flour from 500 g to 487.5 g. To preserve 400 g total water, increase added water from 350 g to 362.5 g. The starter weight remains 100 g and the final hydration remains 72.73%. The total dough weight also remains unchanged if salt is unchanged.
What this conversion does not preserve
Matching the arithmetic does not make two starters biologically identical. A stiff starter can ferment, acidify and mature differently from a liquid starter depending on flour, temperature, feeding ratio and timing. Use the conversion to preserve formula totals, then evaluate fermentation separately.
Use the advanced tool
The homepage includes a starter-hydration conversion tool that performs this adjustment from your own flour, water, starter weight and current hydration. If the requested conversion would require negative added flour or water, the tool stops instead of inventing an impossible ingredient amount.