Compost Tea Brewer Calculator

The calculator divides your brewer's total capacity by (1 + X) to get compost volume, then subtracts that from total capacity to get water volume — so a 50-gallon brewer at a 1:8 ratio uses 50/9 ≈ 5.6 gallons of compost and about 44.4 gallons of water. Compost volume is then converted to cubic feet (÷7.48) to price it against your compost cost per cubic foot.

The formula multiplies water volume — not total brewer capacity — by your ounces-per-gallon rate, reflecting that molasses is dosed as microbial food dissolved into the water portion of the brew rather than scaled to the compost or finished tea volume. Increasing your dilution ratio (more water, less compost) therefore also increases the molasses needed per brew.

It multiplies acres to treat by your application rate in gallons per acre to get total gallons of tea needed, divides that by your brewer's capacity, and rounds the result up to the next full brew cycle since a fractional batch isn't something you can actually run. Separately, "acres per brew" just divides brewer capacity by application rate to show how much ground one full batch covers on its own.

It only totals compost and molasses material costs per brew, multiplies by your planned brews per season, and divides by acres treated — it does not include brewer aeration equipment, electricity to run the pump, or the labor time spent brewing and applying tea. Treat it as a materials-only cost baseline, not a full cost of production.