Compost Calculator
Calculate how much compost you need for your garden, lawn, or raised beds with carbon-to-nitrogen ratio guidance
🌱 Calculate Your Compost Needs
📐 Compost Calculation Formulas
Volume in Cubic Yards
The constant 0.0031 converts square feet × inches into cubic yards
Area Calculations
Rectangle/Square:
Circle:
Carbon to Nitrogen Ratio
Ideal range: 25:1 to 35:1 for optimal microbial activity
Example Calculation
New Vegetable Garden (10 ft × 5 ft):
• Area = 10 × 5 = 50 square feet
• Depth = 2 inches (recommended for vegetables)
• Volume = 50 × 2 × 0.0031 = 0.31 cubic yards
Result: Need approximately 0.31 yd³ (8.4 cubic feet) of compost
📊 Recommended Compost Application Rates
📦 Coverage Reference:
1 cubic yard of compost covers: 324 sq ft at 1" depth | 162 sq ft at 2" depth | 108 sq ft at 3" depth | 81 sq ft at 4" depth
What is Compost?
Compost is decomposed organic matter—a dark, earthy, nutrient-rich material created when microorganisms break down plant debris, food scraps, and other biodegradable materials in the presence of oxygen—transforming waste into "black gold" that enriches soil structure, improves water retention, and provides essential nutrients for plant growth.
The composting process relies on billions of bacteria, fungi, and other microorganisms that consume organic matter, releasing heat (up to 160°F in hot composting) that kills pathogens and weed seeds while creating humus—a stable form of organic matter that improves soil fertility, increases beneficial microbial populations, and helps plants resist diseases and pests naturally.
Compost improves all soil types—it loosens heavy clay for better drainage and root penetration, binds sandy soil to retain moisture and nutrients, and maintains ideal pH balance—making it the single most valuable amendment gardeners can add to their soil, reducing or eliminating the need for synthetic fertilizers while recycling nutrients back into the ecosystem.
⚖️ Carbon to Nitrogen Ratios of Common Materials
⚖️ Balancing Your Compost:
Mix approximately 3 parts brown materials (carbon) with 1 part green materials (nitrogen) by volume for optimal C:N ratio of 25-35:1, promoting fast, hot composting that kills pathogens and weed seeds.
🌍 Benefits of Using Compost
Improves Soil Structure
Compost creates aggregates that improve soil porosity, allowing better air and water movement while supporting beneficial microorganisms—transforms poor soil into thriving ecosystem supporting vigorous root growth and nutrient uptake.
Enhances Water Retention
Organic matter holds 10-20 times its weight in water, reducing irrigation needs by 50% or more—particularly valuable in sandy soils and drought-prone areas, helping plants survive dry periods without constant watering.
Provides Balanced Nutrients
Releases nitrogen, phosphorus, potassium, and micronutrients slowly over months—prevents nutrient leaching and burning that occurs with synthetic fertilizers while supporting sustained plant growth throughout growing season without repeated applications.
Suppresses Plant Diseases
Beneficial microorganisms in compost compete with and suppress soil-borne pathogens—studies show 20-90% reduction in plant diseases when compost is applied, reducing need for fungicides and promoting healthier, more resilient plants.
Reduces Waste
Diverts 30% of household waste from landfills, reducing methane emissions—composting yard waste and food scraps saves money on garbage service while creating valuable resource, closing the nutrient loop in home gardens sustainably.
Sequesters Carbon
Stores atmospheric carbon in stable soil organic matter, mitigating climate change—every ton of compost applied to soil can sequester 0.5-1.0 tons of CO₂ equivalent over time, making composting powerful tool for environmental stewardship.
🔧 Composting Methods
1. Hot Composting (Aerobic)
Timeline: 1-3 months | Temperature: 130-160°F
Active method requiring balanced C:N ratio (25-35:1), regular turning every 3-7 days, and maintained moisture (50-60%)—generates high heat that kills weed seeds, pathogens, and speeds decomposition, producing finished compost quickly ideal for vegetable gardens.
2. Cold Composting (Passive)
Timeline: 6-12 months | Temperature: Ambient
Low-maintenance approach adding materials gradually without turning—relies on slower decomposition at cooler temperatures, doesn't kill all pathogens or weed seeds but eventually produces usable compost with minimal effort, perfect for busy gardeners.
3. Vermicomposting (Worm Bins)
Timeline: 2-6 months | Best for: Indoor/small spaces
Red wiggler worms consume food scraps producing nutrient-rich castings—operates indoors year-round, processes kitchen waste efficiently in compact bins, creates premium soil amendment higher in nutrients than regular compost, ideal for apartments and urban settings.
4. Trench Composting (Direct Burial)
Timeline: 3-12 months | Best for: Large gardens
Bury organic waste directly in garden trenches or holes—materials decompose in place, feeding soil organisms and plant roots directly, eliminates need for separate compost pile, excellent for large quantities of yard waste and kitchen scraps in established gardens.
⚠️ Important Composting Considerations
🚫 Materials to Avoid:
Never compost meat, dairy, oils, pet waste (cats/dogs), diseased plants, or chemically treated materials—these attract pests, create odors, may contain pathogens harmful to humans, or introduce persistent herbicides that damage garden plants even after composting.
💧 Moisture Balance Critical:
Compost should feel like a wrung-out sponge (50-60% moisture)—too dry (< 40%) slows decomposition dramatically, too wet (> 70%) causes anaerobic conditions producing foul ammonia odors and slimy texture. Add water or dry materials to correct imbalances immediately.
🌡️ Temperature Monitoring Important:
Hot compost piles should reach 130-160°F to kill pathogens and weed seeds—temperatures above 160°F kill beneficial microorganisms, below 120°F fail to sanitize materials. Turn pile when temperature drops to reinvigorate decomposition, typically every 3-7 days during active phase.
⏰ Application Timing Matters:
Apply compost 2-4 weeks before planting to allow integration with soil—adding too early wastes nutrients to leaching, too late may temporarily tie up nitrogen during decomposition. Topdress established plants anytime during growing season, avoiding direct contact with stems to prevent rot.
About the Author
Adam
Co-Founder @RevisionTown
Math Expert specializing in diverse international curricula including IB (International Baccalaureate), AP (Advanced Placement), GCSE, IGCSE, and various other educational programs worldwide.
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