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Yeast Pitch Rate Calculator

Enter batch volume, gravity and pitch rate to size your yeast pitch.

How it is calculated

Enter batch volume in litres, original gravity in degrees Plato (°P, not specific gravity such as 1.048) and the target pitch rate in million cells per millilitre per °P. The tool converts litres to millilitres and computes cells (billion) = rate × volume(mL) × °P ÷ 1000. It then divides by 100 to show packs, so it assumes one pack holds 100 billion viable cells; if your yeast has a different count or has aged, scale the pack figure yourself. It also prints the same total written out as a full number of cells. All three inputs must be above zero. The count is for viable cells, so old or poorly stored yeast needs a larger pitch.

Worked example

A 20 L batch at 12 °P with a pitch rate of 0.75 million cells per mL per °P. Volume in millilitres: 20 × 1000 = 20,000. Cells: 0.75 × 20,000 × 12 ÷ 1000 = 180 billion cells. Packs at 100 billion cells each: 180 ÷ 100 = 1.80 packs. In full that is 180,000,000,000 cells. At a pitch rate of 1.5 the same batch would need 360 billion cells, or 3.60 packs.

Try this example →

Common mistakes

  • Entering specific gravity (1.048) instead of degrees Plato (about 12). The result would be roughly twelve times too small, so convert first.
  • Typing the volume in US gallons. The field is litres; 5 gallons is about 19 L.
  • Using the rate for the wrong beer style. Lagers and high-gravity beers are normally pitched at a higher rate than ordinary ales, so the same batch may need twice the cells.
  • Treating the pack count as exact. It assumes 100 billion viable cells per pack, but real packs lose viability with age and heat, so round up or make a starter.
  • Mixing up millions and billions. The rate is in million cells per mL per °P, while the total is shown in billions of cells.

About this calculator

Pitch rate in brewing is the concentration of viable yeast cells added to a batch of wort, and it's one of the biggest levers a brewer has over fermentation character — underpitching stresses the yeast into producing excess esters and fusel alcohols (off-flavors), while overpitching can strip flavor complexity and cause premature flocculation. Pitch rate is conventionally expressed in million cells per milliliter per degree Plato, scaling the target cell count to both the batch's volume and its sugar density (gravity).

This calculator converts your batch volume, original gravity, and target pitch rate into the total number of yeast cells needed and the corresponding number of commercial yeast packs to pitch. It's a practical tool for homebrewers using liquid or dry yeast, especially useful for higher-gravity beers (like imperial stouts or barleywines) that require significantly more yeast than a standard-strength ale to ferment cleanly.

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Comments (1)

  • Editorial team

    Packs cannot be split, so rounding up is the usual choice. In the default 20 L batch the tool says 1.80 packs; two whole packs give about 0.83 million cells per mL per degree Plato instead of 0.75, a slightly heavier pitch than planned. Check the packaging date too, as the count assumes full viability. Which beer style and pitch rate do you use, and do you build a starter first?

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