Yeast Starter Calculator

About this calculator

A yeast starter grows a smaller population of yeast into a healthy, adequately sized pitch before brew day, and the target cell count is driven by batch volume, the wort's original gravity (higher gravity worts need more cells to ferment cleanly) and the pitch rate — commonly cited around 0.75 million cells per mL per degree Plato for ales and roughly double that for lagers, following guidance popularized by yeast researchers like Chris White and Jamil Zainasheff.

Homebrewers use starter calculations whenever they're pitching liquid yeast (which ships with far fewer viable cells than dry yeast) or reusing a yeast slurry from a previous batch, since underpitching leads to slow, incomplete fermentation and off-flavors from stressed yeast, while overpitching can strip desirable esters from beer styles that rely on them.

This calculator takes your batch volume, wort gravity and target pitch rate, and returns the number of yeast cells you need to pitch to hit a healthy fermentation.