Washed Yeast Calculator

Washed Yeast Slurry Calculator

Estimate how many viable cells are in a jar of harvested yeast slurry, and how much of it to pitch for your next batch.

The settled yeast layer only, not the beer/water above it.
Refrigerated slurry loses viability faster than a sealed liquid pack.
Billions — check the Yeast Pitch Rate tool if unsure.
Viable cells available

Cell density: A well-settled washed slurry contains roughly 1 billion cells per ml, though it varies with how thick or diluted it is — use the thickness setting to adjust.

Viability decay: Harvested slurry declines faster than sealed liquid yeast — roughly 20% viability loss per week under refrigeration is a reasonable working assumption, which this calculator uses.

Example: 200ml average slurry, 7 days old → approx 160B viable cells. For a 200B target, pitch roughly 250ml of slurry.

Washing yeast: Always sanitise your jars and utensils before decanting — our no-rinse sanitiser is quick and doesn't need rinsing off before use. Give harvested yeast a sniff and look check before repitching — discard anything with off smells, mould, or unusual colour regardless of what the calculator says.

Need supplies? Grab a No-Rinse Sanitiser for washing jars and a Trial Jar for taking samples. Working from a fresh liquid pack instead? Use the Yeast Viability Calculator. For pitch rate targets and starters, see the Homebrew Calculators hub.