By Dan Smullen
Pitching the right amount of yeast is one of the biggest levers on clean fermentation. Too little and you get a slow, stressed ferment. Enter your gravity, volume and beer type below for the cell count you need.
Calculate your pitch rate
How to read your result
The main figure is the number of viable yeast cells your batch needs, in billions, along with roughly how many standard 100 billion cell packs that is. Compare it against what your yeast supplies: if you are short, a starter or a second pack closes the gap.
Dry yeast usually contains plenty of cells per sachet, so a starter is rarely needed. Liquid yeast, especially older vials, often needs a starter to reach the count, particularly for strong beers and lagers.
Ales, lagers and big beers
Lagers need roughly double the cells of an ale at the same gravity because they ferment cold and slow. Big, high-gravity ales sit in between. Pick the beer type and the calculator applies the right pitch rate for you.
Underpitching shows up as a slow start, more esters, and sometimes off-flavours. Overpitching is far less of a problem, so when in doubt, round up.
Frequently asked questions
How many cells do I need?
The standard targets are about 0.75 million cells per ml per degree Plato for ales and 1.5 for lagers, scaled by batch size and gravity. This calculator turns that into a total billion-cell figure and roughly how many standard packs it is.
What happens if I underpitch?
Too little yeast means a slow start, more stress compounds, and often more esters or off-flavours. Stronger beers and lagers are the least forgiving, which is why they need a bigger pitch or a starter.
Do I need a starter?
If the cell count you need is higher than one fresh pack provides, a yeast starter or a second pack closes the gap. Dry yeast usually contains enough cells per sachet that a starter is not needed.
More homebrewing calculators
This is one tool in the full homebrewing suite. Whatever stage of the brew you are at, there is a calculator for it.