Compost Tea Calculator
Compost tea compost amount and bed coverage from brew size.
What it does
Compost tea stretches good compost across the garden. A pound in five gallons waters a hundred square feet with biology that dry spreading cannot reach evenly.
The tool above sizes the brew. Five gallons regular needs 1 lb of compost for 100 sq ft, brewed a day with stirring. The metric match is 19 L with 0.45 kg for 9.3 m2.
Strength suits the bed. Regular feeds maintained soil, strong wakes tired beds, and stronger than 1 to 3 wastes compost without proven gain.
Brewing needs air and time. Twenty four to 36 hours with stirring or bubbles grows the brew, while stale multi day soup turns against the garden.
Use it fresh. Strain through burlap, water it in the same day, and rinse the brewer so the next batch starts clean.
How to use
- Pick imperial (gal, lb) or metric (L, kg).
- Enter brew water: 5 gal or 19 L suits a can.
- Pick regular or strong.
- Read compost first.
- Read coverage next.
- Brew a day, stir often, water in same day.
Formula
- water
- Brew water volume.
- strength
- Regular or strong brew.
Metric uses 0.45 kg per 19 L regular and 0.49 m2 per liter of coverage. Brew time stays 24 to 36 hours both ways.
Worked example
Example: 5 gal regular brew
Imperial defaults: 5 gal regular brew. These are also the default values, so the page opens on this answer.
- Water: 5 gal, regular strength.
- Compost: 5 / 5 = 1 lb.
- Coverage: 5 x 20 = 100 sq ft.
- Brew: 24 to 36 hours with stirring.
- Tool shows 1 lb, 100 sq ft, Brew 24 to 36 hours, stir often.
Reference table
| Water | Strength | Compost |
|---|---|---|
| 5 gal | Regular | 1 lb |
| 10 gal | Regular | 2 lb |
| 5 gal | Strong | 1.67 lb |
| 19 L | Regular | 0.45 kg |
Limits
- Volume math only. Biology varies by compost.
- Chlorine needs airing first.
- Use same day; storage sours brews.
- Soil tests beat tea for nutrients.
Common mistakes
- Brewing for days until sour.
- Skipping stirring so brews go still.
- Straining never, then clogging cans.
- Watering leaves at noon and scorching.
- Storing brewed tea for next week.
Try it yourself
Quick checks. Answers sit tucked under each question.
10 gal regular?
10 / 5 = 2 lb. Coverage is 10 x 20 = 200 sq ft.
5 gal strong?
5 / 3 = 1.67 lb after rounding. Coverage is 5 x 20 = 100 sq ft.
Questions
Compost for 5 gal?
Divide gallons by 5 regular or 3 strong. Here 5 / 5 = 1 lb.
Coverage?
Multiply gallons by 20. Here 5 x 20 = 100 sq ft.
Regular or strong?
Regular 1 lb per 5 gal suits maintenance, strong 1 per 3 gal suits tired beds. More compost past strong wastes good humus.
Brew time?
Brew 24 to 36 hours with frequent stirring and air. Strain, then water it in the same day.
Does chlorine matter?
Yes. Chlorinated water needs a day of airing first so biology survives the brew.
Does tea fix soil?
No. Disease and nutrient gaps need soil tests.