What is compost?
Compost is decayed organic matter — primarily plant products, such as leaves and apple cores. As plant "waste" products are put together in a pile, they naturally break down and produce a nutrient-rich product that invigorates the microorganisms living in the soil. Compost improves the growth, health, and even taste of produce in home gardens and is also useful for large-scale agriculture or lawns. Whether you need a garden compost calculator or want to figure out how much compost you need for your lawn, our compost calculator can help you determine the right amount.
Why use compost?
Compost improves the quality of your soil and leads to healthy plants. Compost contains nutrients that are beneficial for plants and boosts the food web living within your soil — this includes earthworms, bacteria, and fungi. Although we don't think about these organisms much, they are all critical components to soil health, and a well-balanced food web will allow your plants to take up nutrients more efficiently and possibly withstand disease better.
Using compost as the source of nutrients reduces the need for chemical fertilizers, thereby protecting local lakes, rivers, and oceans. As compost enriches the soil, it also reduces compaction, which decreases the need for irrigation, allows for better drainage, and reduces stormwater runoff.
How much compost should I add to the soil?
If you are working with pure compost, it is best to mix it in with your soil. Typically, you want to go for a 25% compost, 75% soil mixture. If you are working with a garden, raised bed, or a new lawn, you will want to mix about 1–2 inches (2.5–5 cm) of compost into the top 6–8 inches (15–20 cm) of the existing soil. If you add it to an existing lawn, you should add ¼ to ½ of an inch (0.6–1.3 cm) to the top of the lawn before or after aeration. If you are just working on creating a mixture to apply, remember to add about 25% compost to the soil.
Some plants and flower bulbs also thrive in a higher percentage of compost — be sure to do your research before you put them in the ground!
How do I calculate how much compost I need?
To calculate how much compost you need, you first need to know the size of the area you want to cover. Just input the length and width of the space into the compost calculator. Next, you need to know the depth of compost that you require. If you know this amount, input it manually. However, if you are unsure, you can choose your situation (garden, raised bed, new lawn, or established lawn) from the dropdown menu, and the calculator will fill in the recommended depth for you.
The formula is simple:
- Area = Length × Width
- Volume = Area × Depth
The calculator converts all results into cubic yards, cubic feet, cubic meters, and liters so you can purchase the right amount regardless of how compost is sold in your area.
Sample calculation — garden compost
Say you are creating a new garden that will be 10 feet by 5 feet in size. The soil quality is not great, so you want a heavy dosage of compost to mix in with your soil.
- Area = 10 ft × 5 ft = 50 sq. ft
- A new garden with a heavy dosage of compost requires 2 inches of compost.
- Volume = 50 sq. ft × (2/12) ft = 8.33 ft³ ≈ 0.31 yd³
Sample calculation — existing lawn
Let's say your lawn is in much need of some rejuvenation. You are aerating and reseeding your lawn and want to give it a healthy layer of compost as well. The lawn is 110 feet by 80 feet in size.
- Area = 110 ft × 80 ft = 8,800 sq. ft
- Since you are adding on top of an existing lawn, you will add ½ inch of compost to the lawn.
- Volume = 8,800 sq. ft × (0.5/12) ft = 366.7 ft³ ≈ 13.6 yd³
How do I measure compost?
Compost is typically sold by volume — in cubic yards (yd³) or cubic feet (ft³) in the United States, and in cubic meters (m³) or liters (L) in metric countries. One cubic yard equals 27 cubic feet. One cubic meter equals approximately 1.31 cubic yards or 35.3 cubic feet.
Bags of compost at garden centers are commonly sold in 1–3 cubic foot bags, so the calculator helps you determine how many bags to buy. Bulk compost ordered by the truckload is usually priced per cubic yard.
How much will compost cost?
Compost prices vary widely by region and type, but as a general guide:
- Bagged compost — typically $5–$10 per 1 ft³ bag ($135–$270 per yd³)
- Bulk compost — typically $20–$50 per cubic yard
- Premium or specialized compost — can be significantly higher
Use the optional price field in the calculator to enter the price per cubic yard (or cubic meter) and get a total cost estimate for your project.
Composting at home
Making your own compost is a great way to reduce waste and save money on soil amendments. You can compost fruit and vegetable scraps, coffee grounds, eggshells, grass clippings, dried leaves, and cardboard. Avoid adding meat, dairy, or oily foods, as these can attract pests. A well-maintained compost pile or bin will produce finished compost in as little as 2–3 months.