Yeast Pitch Rate Calculator
Calculate how many yeast cells you need for your brew and whether you need a starter. Supports liquid and dry yeast with viability estimation.
Pitch Rate Guide by Style
Different beer styles need different amounts of yeast. Here are the standard rates.
| Style | Rate (M cells/mL/P) |
|---|---|
| Ales (standard) | 0.75 |
| High-gravity Ales | 1 |
| Lagers | 1.5 |
| Hybrid / Kolsch / Alt | 1 |
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How Yeast Pitch Rate Calculation Works
Pitching the right amount of yeast is one of the most important factors in making clean, healthy beer. Under-pitching causes stressed yeast that produce off-flavours. Over-pitching can lead to thin, flavourless beer.
The calculation uses three variables: your wort gravity (converted to degrees Plato), your batch volume, and the style-specific pitch rate.
Cells needed = pitch rate x volume (mL) x degrees PlatoFor ales, the standard rate is 0.75 million cells per millilitre per degree Plato. For lagers, which ferment at lower temperatures and need more yeast to get going, the rate is doubled to 1.5 million.
Liquid Yeast Viability
Liquid yeast loses viability over time. A fresh pack starts at about 97% viable cells and declines roughly 0.7% per day. After a month, you are down to about 76% viability. This is why the manufacture date on the pack matters — older yeast means fewer live cells.
Viability = max(0%, 97% - (days x 0.7%))Yeast Starters
If a single pack does not provide enough cells, you can make a starter. A 1-litre starter on a stir plate will grow roughly 150 billion additional cells. A 2-litre starter yields about 250 billion. The calculator estimates the starter size needed based on the cell deficit.
Dry Yeast
Dry yeast sachets contain roughly 200 billion cells per 11g packet and maintain viability until the expiry date when stored properly. Dry yeast rarely needs a starter — just pitch the right number of packets.
Frequently Asked Questions
How many yeast cells do I need for homebrew?
The standard pitch rate for ales is 0.75 million cells per millilitre per degree Plato. For lagers it is 1.5 million. A typical 20-litre ale at 1.050 OG needs about 186 billion cells. Use the calculator above to get the exact number for your recipe.
What is the difference between liquid and dry yeast?
Liquid yeast packs contain roughly 100 billion cells when fresh, but viability decreases over time at about 0.7% per day. Dry yeast sachets contain roughly 200 billion cells per 11g packet and do not lose significant viability before the expiry date. Dry yeast is often more convenient; liquid yeast offers more strain variety.
Do I need a yeast starter?
You need a starter when a single pack of liquid yeast does not provide enough cells for your batch. This is common for high-gravity beers, lagers, or older yeast packs with reduced viability. A stir plate starter of 1-2 litres can multiply your cell count significantly.
How does yeast viability decrease over time?
Liquid yeast viability declines at roughly 0.7% per day from manufacture. A fresh pack starts at about 97% viability. After one month (30 days) viability drops to about 76%. After two months it is around 55%. After three months only about 33%. Old yeast can still be used, but you will need more packs or a larger starter.
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