Homebrew Yeast Pitch, Priming & Fermentation Pressure Calculator

Calculate yeast pitch rates, priming sugar, force carbonation PSI, and fermentation metrics for your next brew.

Last reviewed: June 2026
Built and maintained by · Last updated June 2026

Batch Details

gal

Yeast Starter

Pitch Results

Cells Needed
-
Cells Available
-
Pitch Status
-
Yeast Viability
-
Recommended Packs (no starter)
-
Recommended Starter
-

Gravity Readings

°F

Fermentation Results

ABV
-
Apparent Attenuation
-
Calories per 12oz
-
Original Gravity
-
in degrees Plato
Final Gravity
-
in degrees Plato

Carbonation Target

°F
gal

Carbonation Results

Residual CO2
-
dissolved CO2 already in beer
CO2 to Add
-
Corn Sugar Amount
-
Sugar per Liter
-

CO2 Volumes by Beer Style

British Ales
1.5 - 2.0
American Ales
2.2 - 2.8
German Lagers
2.4 - 2.8
Belgian Ales
2.8 - 4.5
Hefeweizen
3.3 - 4.5
Important Disclaimer: This calculator estimates brewing math from simplified formulas and assumptions. Verify carbonation targets, package pressure limits, yeast handling, sanitation, and fermentation temperature before packaging or serving beer.

How the Homebrew Calculator works

This calculator groups three common brewing checks into one page: yeast pitch, fermentation readings, and priming or keg carbonation. The pitch tab estimates how many yeast cells a batch needs from volume, original gravity, and pitch rate. The fermentation tab converts original and final gravity into ABV, apparent attenuation, degrees Plato, and estimated calories. The priming tab estimates residual CO2, sugar weight, force-carbonation pressure, and spunding pressure from temperature and target carbonation.

The pitch calculation converts specific gravity to degrees Plato and applies cells needed = pitch rate * volume in mL * degrees Plato. Results are shown in billions of cells. Liquid yeast defaults to 100B cells per pack, dry yeast to 200B cells per pack, and the optional production date reduces liquid yeast viability over time. Starter estimates are simple growth estimates, with a higher growth rate when a stir plate is selected.

Yeast pitch workflow

  • Set batch volume: Use gallons or liters. The calculator converts the value internally before estimating cells needed.
  • Enter original gravity: Higher gravity wort needs more cells because there is more extract for the yeast to ferment.
  • Choose ale or lager: Ale defaults to 0.75 million cells per mL per degree Plato; lager defaults to 1.50.
  • Check viability and starter size: Older liquid yeast may need extra packs or a starter. Dry yeast defaults to high viability.

Fermentation readings

Use the fermentation tab after you have original and final gravity readings. ABV is estimated with (OG - FG) * 131.25, apparent attenuation compares the gravity drop to the original extract, and the calories estimate combines alcohol and residual extract for a 12 oz serving. These numbers are useful for batch notes, recipe comparison, and spotting a stuck fermentation.

Priming and carbonation

The priming tab estimates how much CO2 is already dissolved in the beer from the packaging temperature. It subtracts that residual carbonation from your target volumes and converts the remaining CO2 into grams of corn sugar, table sugar, DME, or honey. If you choose keg or spunding mode, the calculator instead shows the pressure needed at the selected temperature for the same target carbonation.

Common mistakes

  • Using fermentation temperature for priming: Use the warmest beer temperature after fermentation for residual CO2, not necessarily the current room temperature.
  • Ignoring yeast age: A single old liquid pack may look adequate by label count but under-pitch after viability loss.
  • Mixing gravity units: Enter specific gravity values such as 1.050, not Plato, in the OG and FG fields.
  • Over-carbonating bottles: Keep target CO2 volumes appropriate for the beer style and packaging strength.

Example

For a 5 gallon ale at 1.050 OG and a 0.75 M cells/mL/degree Plato pitch rate, the calculator estimates roughly 176B cells needed. One fresh liquid pack provides about 95B cells after the default viability adjustment, so the result is under-pitched unless you add packs or a starter. For the same 5 gallon batch packaged at 65 F to 2.5 volumes of CO2, the priming tab estimates about 45 g of corn sugar, or roughly 1.6 oz.

Frequently Asked Questions

It estimates yeast cells needed and available, fermentation metrics from OG and FG, priming sugar for bottles, force carbonation PSI, and spunding valve PSI.
The defaults are 0.75 million cells per mL per degree Plato for ales and 1.50 for lagers. You can override the pitch rate for high-gravity, cold-fermented, or intentionally low-pitch recipes.
Liquid yeast viability declines with age. Entering the production date lets the calculator reduce the estimated live cells and show whether a starter or extra pack is likely needed.
Use the warmest temperature the beer reached after fermentation, because that determines how much CO2 is still dissolved before packaging.
No. It is a brewing math aid. Recipe design, sanitation, yeast health, oxygen exposure, package strength, and temperature control still determine the finished beer.

Quick reference

Homebrew Yeast Pitch, Priming & Fermentation Pressure Calculator — quick reference
AspectDetail
PurposeHomebrew Yeast Pitch, Priming & Fermentation Pressure Calculator is a free browser calculator for fast, repeatable estimates.
Runs inAny modern browser — no install, no signup.
PrivacyInputs are computed locally; nothing is uploaded.
Best forQuick estimates, daily reference, study, planning.