5 gal × 0.10 ratio × 8.34 lbs/gal = 4.17 lbs. 4.17 / 0.5 lbs per cup = 8.34, rounds to 8 cups. Molasses = 5 × 1.0 oz/gal = 5.0 oz. Coverage = 5 / 0.02 = 250 sq ft.

23-Gallon Worm Casting Tea, Foliar Spray

Inputs

Compost TypeWorm Castings

Batch Size3 gallons

AdditiveKelp Meal

ApplicationFoliar Spray (1:4)

Result

Compost Needed4 cups

Kelp Meal0.8 oz

Brew Time18 hr

Coverage600 sq ft

3 × 0.08 × 8.34 = 2.0 lbs. 2.0 / 0.5 = 4 cups. Kelp = 3 × 0.25 = 0.75 oz. Coverage = 3 / 0.005 = 600 sq ft.

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Frequently Asked Questions

What is the ratio for compost tea?

The standard compost-to-water ratio is 10% by weight for general aged compost — about 4.2 lbs (8 cups) of compost per 5 gallons of water. Worm castings use a lighter 8% ratio (3.3 lbs per 5 gallons), while fungal-dominant recipes use 12% for stronger inoculation.

General compost: 10% ratio — ~8 cups per 5 gallons
Worm castings: 8% ratio — lighter, faster brewing
Fungal-dominant: 12% ratio — more material, longer brew
Bacterial-dominant: 10% ratio — green compost, shorter brew
Always use finished, mature compost — not fresh or hot compost

Compost Type	Ratio to Water	Brew Time
General Aged	10%	24 hours
Worm Castings	8%	18 hours
Fungal-Dominant	12%	36 hours
Bacterial-Dominant	10%	20 hours

How long should compost tea brew?

Most compost tea brews for 18–36 hours with active aeration. General compost tea is ready in 24 hours. Worm casting tea brews faster at 18 hours. Fungal-dominant tea needs 36 hours for fungal hyphae to develop. Do not brew longer than 48 hours — anaerobic bacteria take over and produce harmful compounds.

18 hours: worm casting tea (fastest)
20 hours: bacterial-dominant (green compost)
24 hours: general aged compost (standard)
36 hours: fungal-dominant (woody compost)
Maximum 48 hours — use immediately after brewing

What additives should I add to compost tea?

Unsulfured molasses is the most common additive at 1 oz per gallon — it feeds beneficial bacteria and accelerates multiplication. Fish hydrolysate (0.5 oz/gal) adds nitrogen and feeds fungi. Kelp meal (0.25 oz/gal) provides micronutrients and growth hormones. Humic acid (0.5 oz/gal) improves nutrient uptake.

Molasses: 1 oz/gal — feeds bacteria, most common additive
Fish hydrolysate: 0.5 oz/gal — feeds fungi, adds nitrogen
Kelp meal: 0.25 oz/gal — trace minerals and plant hormones
Humic acid: 0.5 oz/gal — improves nutrient availability
Never use sulfured molasses — sulfur kills beneficial microbes

How much compost tea do I need for my garden?

For soil drenching, apply 0.02 gallons per sq ft — a 5-gallon batch covers 250 sq ft. For foliar spray (diluted 1:4 with water), 5 gallons of concentrate covers 1,000 sq ft. Apply every 2–4 weeks during the growing season for best results.

Soil drench: 0.02 gal/sq ft — 5 gallons covers 250 sq ft
Foliar spray: 0.005 gal/sq ft (diluted 1:4) — 5 gal covers 1,000 sq ft
Transplant soak: 0.05 gal/sq ft — heavier application for new plantings
Apply every 2–4 weeks during growing season
Best time: early morning or evening (avoid midday sun on leaves)

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Last Updated: Jul 2, 2026

This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.

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