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Compost Calculator
Two modes: estimate compost yards for top-dressing or amending, or balance a C:N ratio between browns and greens for a hot pile.
Compost details
Compost needed
0.65 cu yd
17.5 cu ft over 100 sq ft (9.3 sq m)
- Bags needed
- 12 bags of 1.5 cu ft
- Weight
- 1,225 lb
- Weight (metric)
- 556 kg
- Weight (tons)
- 0.61 tons
- Net volume
- 0.62 cu yd
- Cubic meters
- 0.47 cu m
1/4 to 1/2 inch top-dressing is recommended for lawns; more can smother grass. Use 1 to 3 inches for garden beds.
Frequently Asked Questions about the Compost Calculator
How much compost do I need to top-dress my lawn?
Top-dressing rates are 1/4 to 1/2 inch deep. For 1,000 sq ft at 1/4 in: 1000 x (0.25/12) = 20.8 cu ft, about 0.77 cu yd. For amending garden beds, aim for 2-3 inches incorporated into the top 6 in of soil.
What is the C:N ratio and why does it matter?
Carbon to nitrogen ratio. Hot composting works best at C:N of about 25-30:1. Too much carbon (high ratio) and the pile stalls; too much nitrogen (low ratio) and the pile turns smelly and loses nitrogen as ammonia. The calculator helps you blend browns and greens to hit the sweet spot.
What are browns and greens?
Browns are high-carbon: dry leaves (60:1), straw (75:1), cardboard (350:1), wood chips (400:1). Greens are high-nitrogen: grass clippings (15:1), food scraps (15:1), coffee grounds (20:1), fresh manure (varies, 7-25:1). Mix about 3 parts browns to 1 part greens by volume to land near 25:1.
How long does it take to make compost?
Hot, well-managed piles: 4-8 weeks. Cold, neglected piles: 6-12 months. The difference comes from temperature, moisture, particle size, and turning frequency. Hot composting (above 130 F) also kills weed seeds and pathogens.
Can I use compost straight on plants?
Yes, once it is finished (dark, crumbly, earthy-smelling, no recognizable scraps). Unfinished compost can tie up nitrogen as it continues to break down and may stunt plants. If in doubt, let it cure another month or use it as mulch instead of mixing in.