Brewing · Pitch Rate
Enter batch size, gravity, and beer type to get the cells to pitch, the number of fresh packs, and dry yeast grams — live as you type.
Worked example
≈ 186 B cells
Lagers need double — switch beer type live below.
Live calculator · updates as you type
Target rate is 0.75 million cells per mL per °Plato (12.4 °P here). Dry-yeast count assumes ~20 billion viable cells per gram; liquid packs assume ~100 billion each. Adjust for yeast age and viability.
Cells to pitch
Pitch rate by beer type
Pitch rate guide
Most fermentation faults trace back to too little healthy yeast. This guide shows how to hit the right cell count and when a starter is worth the extra day.
Million cells per mL per °Plato for ales.
Double the ale rate for cold fermentation.
Cells in a new liquid pack or vial.
The target scales with both volume and gravity, then divides into packs or grams. Bigger or stronger beers simply need more cells to finish clean.
Pick your beer type, set your volume units, then enter batch size and original gravity. The calculator returns the target cell count in billions, how many fresh liquid packs that is, and the equivalent grams of dry yeast — updating live as you change any input.
Beer type sets the pitch rate: ales pitch lighter, lagers heavier because they ferment cold. Use your measured or estimated original gravity, since higher gravity needs proportionally more cells.
Pitch rate is cells per millilitre per degree Plato. It scales with both how much wort you have and how much sugar is in it, because a bigger, sweeter batch gives the yeast more work and needs a bigger, healthier population to do it cleanly.
The common targets are about 0.75 million cells per mL per °P for ales and 1.5 for lagers. High-gravity beers sit in between to above the ale rate. These are starting points; adjust for how much ester or clean character you want.
The target cell count is the pitch rate times volume times gravity. Turning that into what you buy is the practical part: a fresh liquid pack is roughly 100 billion cells, and dry yeast holds about 20 billion viable cells per gram.
That is why one 11-gram dry sachet covers many standard ales without a starter, while the same beer from a single ageing liquid pack would underpitch. The calculator shows both routes so you can pick what you have.
Make a starter whenever a single fresh pack falls short of the target — typically for gravities above about 1.055, for any lager, or when your yeast is past its freshest.
A starter grows the population on a small amount of wort a day or two before brewing, so you pitch active, healthy yeast at the right count instead of stressing an underpitched batch.
Underpitching is the more common mistake and the more damaging one: too few cells means a slow start, more stress compounds, and off-flavours like excess fusel alcohol. Hitting the target keeps fermentation clean and predictable.
A modest overpitch is usually harmless and can even help lagers, though a very large overpitch can mute the yeast character you want in styles that rely on it. Aim for the calculated number rather than eyeballing it.
Common questions about cell counts, packs, starters, and pitching.
Pitch rate is how many yeast cells you add per volume of wort and per degree Plato of gravity, usually expressed in million cells per millilitre per °Plato. The standard ale rate is about 0.75, and lagers roughly double it to 1.5 because they ferment cold and need more cells to finish cleanly.
Multiply the pitch rate by your batch volume in millilitres and your original gravity in degrees Plato. A 20-litre ale at 1.050 (about 12.4 °P) needs roughly 186 billion cells. This calculator does the maths and also converts that into liquid packs and dry yeast grams.
A fresh liquid pack or vial holds about 100 billion cells when new, so that 20-litre ale needs roughly two fresh packs — or one pack grown up in a starter. Cell counts drop as yeast ages, so older packs need a starter or an extra pack to hit the target.
Make a starter when a single fresh pack falls short of the target cell count — common for gravities above about 1.055, for lagers, and for older yeast. A starter multiplies the cells before brew day so you pitch a healthy, active population instead of underpitching.
Underpitching stresses the yeast, which can cause slow or stuck fermentation, excess esters and fusel alcohols, and off-flavours. Overpitching by a small margin is generally safer than underpitching, though grossly overpitching can mute desirable character. Aim for the target rather than guessing.
Dry yeast is dense — roughly 20 billion viable cells per gram — so many ales are covered by a single 11-gram sachet without a starter. The calculator estimates the grams needed from your target cell count; round up to whole sachets and rehydrate if the manufacturer recommends it.