---
title: "Compost Tea Dilution Calculator: Get Your Dilution Ratio Right Before You Kill Your Microbes"
canonical: "https://theyieldgrid.com/compost-tea-recipe/"
model_id: "tyg-553"
model_version: "1.0.0"
last_reviewed: "2026-08-24T08:35:29"
reviewed_by: "Umer Hayiat"
---

# Compost Tea Dilution Calculator: Get Your Dilution Ratio Right Before You Kill Your Microbes

> Canonical calculator: [https://theyieldgrid.com/compost-tea-recipe/](https://theyieldgrid.com/compost-tea-recipe/)

## What this calculator does

Home - Free Gardening Calculators & Tools - Compost Tea Dilution Calculator: Get Your Dilution Ratio Right Before You Kill Your Microbes Aerated compost tea (AACT) delivers billions of beneficial microorganisms to plant roots and leaf surfaces, but those microbes die within minutes of contact with chlorinated water or incorrect dilution. The difference between a thriving soil food web and an expensive bucket of dead bacteria comes down to two numbers: your dilution ratio and your water preparation time.

## Inputs

| Input | ID | Type | Unit | Range or choices | Required |
|---|---|---|---|---|---|
| Tea Volume (Gallons of concentrate) | `composttea_volume` | number | Gallons of concentrate | 0.1 to | Yes |
| Concentrate Strength | `composttea_strength` | select |  | Select strength… = ``; Strong (24+ hr brew) = `strong`; Weak (12-18 hr brew) = `weak` | No |
| Foliar Spray | `composttea_app_foliar` | radio |  |  | No |
| Root Drench | `composttea_app_root` | radio |  |  | No |

## Outputs

| Output ID | Default state |
|---|---|
| `composttea_results` | 0 Gallons of Water Needed Dilution Ratio Visualization 1:10 Tea Water Component Amount Recommended Additives (per gallon of tea) Quick Reference Table Tea Vol Foliar (1:10) Root Weak (1:20) Root Strong (1:5) 1 gal 10 gal 20 gal 5 gal 2 gal 20 gal 40 gal 10 gal 3 gal 30 gal 60 gal 15 gal 5 gal 50 gal 100 gal 25 gal 10 gal 100 gal 200 gal 50 gal |
| `composttea_out_primary` | 0 |
| `composttea_warnings` |  |

## Formula and method

Show the calculation steps Step 1: Determine the dilution ratio based on inputs Foliar spray (any strength): Ratio = 1:10 Root drench + Strong concentrate: Ratio = 1:5 Root drench + Weak concentrate: Ratio = 1:20 Step 2: Calculate water needed Water Needed = Tea Volume x Ratio Number Example: 5 gallons tea x 10 (for foliar) = 50 gallons water The calculator selects between three fixed ratios based on your inputs, ensuring foliar sprays stay gentle while root drenches deliver appropriate microbial density. Step 3: Calculate total mix volume Total Mix = Tea Volume + Water Needed Example: 5 + 50 = 55 gallons total Step 4: Calculate additive recommendations Molasses = Tea Volume x 2 tablespoons per gallon Kelp = Tea Volume x 1 teaspoon per gallon Rounding: All outputs display one decimal place. Gallons are not converted to other units. Assumptions and Limits The calculator assumes you have brewed aerated compost tea (AACT) using the standard method: compost in a mesh bag, submerged in water, with continuous air bubbling for 12-36 hours. Ratios are based on commonly cited AACT application guidelines, not laboratory-verified microbial counts for your specific tea. The tool does not account for tea age. Compost tea should be used within 4-6 hours of stopping aeration; microbial populations decline rapidly after that. Water temperature is not factored in. Ideal brewing and mixing temperatures range from 55-75 degrees F; cold water slows microbial activity, hot water kills microbes. Additive amounts (molasses, kelp) are recommendations for the brewing phase, not for post-dilution addition. The calculator assumes static brewing conditions. Variables like compost source quality, aeration rate, and ambient temperature significantly affect actual microbial density. Results apply to liquid application only. This tool does not calculate compost tea for soil injection or drip irrigation systems that may require different concentrations. For adjusting soil chemistry before application, the soil pH lime calculator or soil pH sulfur calculator can help establish optimal growing conditions.

## Verified worked examples

### Scenario 1: Small Garden Foliar Spray

Tea Volume: 2 gallons Concentrate Strength: Strong (24+ hour brew) Application Method: Foliar Spray Result: 20 gallons of water needed. Total mix: 22 gallons at 1:10 dilution. This volume covers approximately 2,000-3,000 square feet of leaf surface when applied with a pump sprayer until leaves glisten but do not drip. Once the calculator determines your water volume, application becomes straightforward: spray until leaves glisten without dripping, then move to the next section. Apply in early morning or late evening to prevent rapid evaporation.

### Scenario 2: Raised Bed Root Drench with Strong Concentrate

Tea Volume: 5 gallons Concentrate Strength: Strong Application Method: Root Drench Result: 25 gallons of water needed. Total mix: 30 gallons at 1:5 dilution. The 1:5 ratio delivers a potent microbial dose suitable for established plants. Apply 1-2 gallons of diluted tea per 10 square feet of soil surface. For help calculating soil volumes in raised beds, see the raised bed soil calculator .

### Scenario 3: Seedling Application with Weak Concentrate

Tea Volume: 1 gallon Concentrate Strength: Weak (14 hour brew) Application Method: Root Drench Result: 20 gallons of water needed. Total mix: 21 gallons at 1:20 dilution. The 1:20 ratio protects tender seedling roots from potential nutrient or microbial overload. This conservative dilution is appropriate when brew quality is uncertain or when treating young transplants.

## Assumptions

Show the calculation steps Step 1: Determine the dilution ratio based on inputs Foliar spray (any strength): Ratio = 1:10 Root drench + Strong concentrate: Ratio = 1:5 Root drench + Weak concentrate: Ratio = 1:20 Step 2: Calculate water needed Water Needed = Tea Volume x Ratio Number Example: 5 gallons tea x 10 (for foliar) = 50 gallons water The calculator selects between three fixed ratios based on your inputs, ensuring foliar sprays stay gentle while root drenches deliver appropriate microbial density. Step 3: Calculate total mix volume Total Mix = Tea Volume + Water Needed Example: 5 + 50 = 55 gallons total Step 4: Calculate additive recommendations Molasses = Tea Volume x 2 tablespoons per gallon Kelp = Tea Volume x 1 teaspoon per gallon Rounding: All outputs display one decimal place. Gallons are not converted to other units. Assumptions and Limits The calculator assumes you have brewed aerated compost tea (AACT) using the standard method: compost in a mesh bag, submerged in water, with continuous air bubbling for 12-36 hours. Ratios are based on commonly cited AACT application guidelines, not laboratory-verified microbial counts for your specific tea. The tool does not account for tea age. Compost tea should be used within 4-6 hours of stopping aeration; microbial populations decline rapidly after that. Water temperature is not factored in. Ideal brewing and mixing temperatures range from 55-75 degrees F; cold water slows microbial activity, hot water kills microbes. Additive amounts (molasses, kelp) are recommendations for the brewing phase, not for post-dilution addition. The calculator assumes static brewing conditions. Variables like compost source quality, aeration rate, and ambient temperature significantly affect actual microbial density. Results apply to liquid application only. This tool does not calculate compost tea for soil injection or drip irrigation systems that may require different concentrations. For adjusting soil chemistry before application, the soil pH lime calculator or soil pH sulfur calculator can help establish optimal growing conditions. The calculator assumes you have brewed aerated compost tea (AACT) using the standard method: compost in a mesh bag, submerged in water, with continuous air bubbling for 12-36 hours. Ratios are based on commonly cited AACT application guidelines, not laboratory-verified microbial counts for your specific tea. The tool does not account for tea age. Compost tea should be used within 4-6 hours of stopping aeration; microbial populations decline rapidly after that. Water temperature is not factored in. Ideal brewing and mixing temperatures range from 55-75 degrees F; cold water slows microbial activity, hot water kills microbes. Additive amounts (molasses, kelp) are recommendations for the brewing phase, not for post-dilution addition. The calculator assumes static brewing conditions. Variables like compost source quality, aeration rate, and ambient temperature significantly affect actual microbial density. Results apply to liquid application only. This tool does not calculate compost tea for soil injection or drip irrigation systems that may require different concentrations. For adjusting soil chemistry before application, the soil pH lime calculator or soil pH sulfur calculator can help establish optimal growing conditions. Critical Warnings: Chlorine destroys compost tea. Municipal tap water contains chlorine or chloramine that kills beneficial microbes on contact. Let tap water sit uncovered for 24+ hours to allow chlorine to off-gas, or use collected rainwater, well water, or dechlorinated water from an aquarium supply. Do not store diluted tea. Use the entire batch within 4-6 hours of mixing. Diluted tea without aeration becomes anaerobic and can harbor harmful pathogens. Foliar application on edibles requires timing. Stop foliar spraying at least 2 weeks before harvest to allow microbial residue to dissipate. Over-concentration causes damage. Using ratios stronger than 1:5 can overwhelm plant roots or cause foliar burn. When in doubt, dilute more. Minimum Standards: Brew time minimum: 12 hours with active aeration (visible bubbling throughout) Aeration requirement: Continuous air supply producing at least 0.05 CFM per gallon of tea Compost-to-water ratio for brewing: Approximately 1:5 to 1:10 (compost to water by volume) Application frequency: No more than once per week for most plants; biweekly for sensitive species Competitor Trap: Many compost tea guides omit the critical distinction between strong and weak concentrates when recommending root drench ratios. A 1:5 dilution applied to a weak tea delivers insufficient microbes, while a 1:20 dilution applied to a strong tea wastes potency. This calculator adjusts the ratio based on your actual brew strength, preventing both under-application and resource waste.

## Limitations and safety

The calculator assumes you have brewed aerated compost tea (AACT) using the standard method: compost in a mesh bag, submerged in water, with continuous air bubbling for 12-36 hours. Ratios are based on commonly cited AACT application guidelines, not laboratory-verified microbial counts for your specific tea. The tool does not account for tea age. Compost tea should be used within 4-6 hours of stopping aeration; microbial populations decline rapidly after that. Water temperature is not factored in. Ideal brewing and mixing temperatures range from 55-75 degrees F; cold water slows microbial activity, hot water kills microbes. Additive amounts (molasses, kelp) are recommendations for the brewing phase, not for post-dilution addition. The calculator assumes static brewing conditions. Variables like compost source quality, aeration rate, and ambient temperature significantly affect actual microbial density. Results apply to liquid application only. This tool does not calculate compost tea for soil injection or drip irrigation systems that may require different concentrations. For adjusting soil chemistry before application, the soil pH lime calculator or soil pH sulfur calculator can help establish optimal growing conditions. Critical Warnings: Chlorine destroys compost tea. Municipal tap water contains chlorine or chloramine that kills beneficial microbes on contact. Let tap water sit uncovered for 24+ hours to allow chlorine to off-gas, or use collected rainwater, well water, or dechlorinated water from an aquarium supply. Do not store diluted tea. Use the entire batch within 4-6 hours of mixing. Diluted tea without aeration becomes anaerobic and can harbor harmful pathogens. Foliar application on edibles requires timing. Stop foliar spraying at least 2 weeks before harvest to allow microbial residue to dissipate. Over-concentration causes damage. Using ratios stronger than 1:5 can overwhelm plant roots or cause foliar burn. When in doubt, dilute more. Minimum Standards: Brew time minimum: 12 hours with active aeration (visible bubbling throughout) Aeration requirement: Continuous air supply producing at least 0.05 CFM per gallon of tea Compost-to-water ratio for brewing: Approximately 1:5 to 1:10 (compost to water by volume) Application frequency: No more than once per week for most plants; biweekly for sensitive species Competitor Trap: Many compost tea guides omit the critical distinction between strong and weak concentrates when recommending root drench ratios. A 1:5 dilution applied to a weak tea delivers insufficient microbes, while a 1:20 dilution applied to a strong tea wastes potency. This calculator adjusts the ratio based on your actual brew strength, preventing both under-application and resource waste.

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## Provenance

- Model ID: `tyg-553`
- Model version: `1.0.0`
- Reviewed by: Umer Hayiat
- Page modified: 2026-08-24T08:35:29
- Runtime SHA-256: `843ca99e49439c90ee8b34b88b31a44c8bba6c4e2bbf5f442cc7dc8d23ff2fd1`

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