Compost Tea Brewer Calculator

Calculate compost tea brewing ratios, material quantities, coverage per brew, and seasonal application costs for actively aerated compost tea (AACT).

Inputs

Brewer Capacity (gallons)

Compost Dilution Ratio (1:X)

Acres to Treat

Application Rate (gal/acre)

Brews Per Season

Compost Cost ($/cu ft)

Molasses (oz/gal water)

Molasses Cost ($/gallon)

Tab to move between fields

Results

Compost Needed (cu ft)

0.74

Acres Per Brew

Water Needed (gallons)44.4

Molasses Needed (oz)44.4

Material Cost Per Brew$25.06

Season Cost Per Acre$15.04

Brews For Coverage2%

Cost Per Acre Per Application$5.01

How to Use This Calculator

Enter brewer capacity (gallons) and compost dilution ratio (1:X, e.g., 8 for a 1:8 ratio) — typical ratios run 1:5 to 1:10.
Enter acres to treat, application rate (gallons per acre), and brews per season.
Enter compost cost per cubic foot, molasses use rate (oz per gallon of water), and molasses cost per gallon.
Read compost, water, and molasses quantities needed per brew, along with acres covered per brew.
Review material cost per brew, cost per acre per application, brews needed for full coverage, and season cost per acre.

How the result changes with Brewer Capacity (gallons)

Brewer Capacity (gallons)	Compost Needed (cu ft)	Acres Per Brew
501	7.44	50.1
1,751	26.01	175.1
3,250	48.28	325
4,500	66.84	450

What each input means

Brewer Capacity (gallons): Total brewer tank capacity in gallons.
Compost Dilution Ratio (1:X): Parts water per part compost (e.g., 8 = 1:8 ratio). Typical: 5-10.
Acres to Treat: Total acreage to be treated per brewing session.
Application Rate (gal/acre): Gallons of finished tea per acre (foliar: 5-10, soil drench: 10-20).
Brews Per Season: Number of times you brew during the growing season.
Compost Cost ($/cu ft): Cost per cubic foot of quality finished compost.
Molasses (oz/gal water): Unsulfured molasses as microbial food source (typically 1 oz/gal).
Molasses Cost ($/gallon): Cost per gallon of unsulfured blackstrap molasses.

What each result means

Compost Needed (cu ft): Cubic feet of compost per brew based on dilution ratio.
Water Needed (gallons): Gallons of non-chlorinated water per brew.
Molasses Needed (oz): Ounces of molasses per brew.
Acres Per Brew: Acreage covered by one full brewer batch.
Material Cost Per Brew: Compost + molasses cost per brewing session.
Season Cost Per Acre: Total compost tea cost per acre over the season.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Brewer Capacity (gallons) = 50, Compost Dilution Ratio (1:X) = 8, Acres to Treat = 10, Application Rate (gal/acre) = 10 = 8 input(s) provided
Calculate Compost Needed
Compost Needed = compostVolumeGal / 7.48
0.74 = 0.74
Calculate Acres Per Brew
Acres Per Brew = brewerGallons / applicationRate
5 = 5
Calculate Water Needed
Water Needed = brewerGallons - compostVolumeGal
44.4 = 44.4
Calculate Molasses Needed
Molasses Needed = waterVolumeGal * molassesOzPerGal
44.4 = 44.4

Engine last updated August 6, 2026. Checked against 1 independently-derived test — how we verify calculators.

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