Uses the compost amount and bag size from the first tab. Enter prices from your local garden centre and landscape supplier.
| Option | Quantity | Total | Cost per |
|---|
| Ingredient | % | cu ft | cu yd | litres | m³ |
|---|
| Material | cu ft | cu yd | litres | m³ |
|---|
Bag count uses the bag size from the Compost amount tab. The other ingredients are the rest of the mix: split them in the Soil mix ratio tab.
| Unit | Result |
|---|
Quick answers
How to calculate how much compost you need
Compost is sold by volume, so every estimate starts with the same step: area multiplied by depth. Measure the length and width of the area in feet, decide how deep the layer should be, and convert the result into cubic yards (bulk) or bags.
Cubic yards = area (sq ft) × depth (in) ÷ 324
Bags = cubic feet ÷ bag size (cu ft), rounded up
The 324 comes from 27 cubic feet in a cubic yard times 12 inches in a foot. Cornell Waste Management Institute publishes the same estimate with a rounded factor of 0.0031 (area × depth × 0.0031 = cubic yards).
Worked examples
- 100 sq ft vegetable bed, 2 in layer: 100 × 2 ÷ 324 = 0.62 cubic yards, or 16.7 cubic feet. That is 12 bags of 1.5 cu ft.
- 200 sq ft garden, 3 in layer: 200 × 3 ÷ 324 = 1.85 cubic yards. With 10% extra, order about 2 cubic yards.
- 1,000 sq ft lawn, ¼ in top-dressing: 1,000 × 0.25 ÷ 324 = 0.77 cubic yards.
- Round bed, 10 ft across, 3 in layer: area = 3.1416 × 5² = 78.5 sq ft, so 78.5 × 3 ÷ 324 = 0.73 cubic yards.
Add about 10% to the final figure. Ground is rarely level and compost settles after watering.
Compost coverage chart: how far does one cubic yard go?
| Depth | 1 cu yd covers | Cu yd per 100 sq ft | Cu yd per 1,000 sq ft | Typical use |
|---|---|---|---|---|
| ¼ in | 1,296 sq ft | 0.08 | 0.77 | Lawn top-dressing |
| ½ in | 648 sq ft | 0.15 | 1.54 | Heavier lawn top-dressing |
| 1 in | 324 sq ft | 0.31 | 3.09 | Annual mulch-style dressing |
| 2 in | 162 sq ft | 0.62 | 6.17 | Garden bed top-dressing |
| 3 in | 108 sq ft | 0.93 | 9.26 | Soil improvement before planting |
| 4 in | 81 sq ft | 1.23 | 12.35 | New beds, poor soil |
| 6 in | 54 sq ft | 1.85 | 18.52 | Building a new bed layer |
Metric coverage
| Depth | 1 m³ covers | m³ per 10 m² | m³ per 100 m² |
|---|---|---|---|
| 1 cm | 100 m² | 0.10 | 1.0 |
| 2.5 cm | 40 m² | 0.25 | 2.5 |
| 5 cm | 20 m² | 0.50 | 5.0 |
| 7.5 cm | 13.3 m² | 0.75 | 7.5 |
| 10 cm | 10 m² | 1.00 | 10.0 |
| 15 cm | 6.7 m² | 1.50 | 15.0 |
Rule of thumb: 2 to 3 inches (5 to 7.5 cm) a year is enough for most garden beds. Mix compost into the soil rather than planting in pure compost.
How much compost for common garden sizes?
Quick lookup for top-dressing or amending an existing bed. Bag counts use 1.5 cu ft bags and already round up. Add about 10% extra.
| Area | Sq ft | 2 in layer | 3 in layer |
|---|---|---|---|
| 4 × 4 ft | 16 | 0.10 cu yd · 2.7 cu ft · 2 bags | 0.15 cu yd · 4.0 cu ft · 3 bags |
| 3 × 6 ft | 18 | 0.11 cu yd · 3.0 cu ft · 2 bags | 0.17 cu yd · 4.5 cu ft · 3 bags |
| 4 × 8 ft | 32 | 0.20 cu yd · 5.3 cu ft · 4 bags | 0.30 cu yd · 8.0 cu ft · 6 bags |
| 4 × 12 ft | 48 | 0.30 cu yd · 8.0 cu ft · 6 bags | 0.44 cu yd · 12.0 cu ft · 8 bags |
| 10 × 10 ft | 100 | 0.62 cu yd · 16.7 cu ft · 12 bags | 0.93 cu yd · 25.0 cu ft · 17 bags |
| 12 × 12 ft | 144 | 0.89 cu yd · 24.0 cu ft · 16 bags | 1.33 cu yd · 36.0 cu ft · 24 bags |
| 10 × 20 ft | 200 | 1.23 cu yd · 33.3 cu ft · 23 bags | 1.85 cu yd · 50.0 cu ft · 34 bags |
How much soil and compost to fill a raised bed
Totals are for a completely empty bed. The compost column assumes compost is 30% of the mix (the 60/30/10 recipe) and uses 1.5 cu ft bags. Add 10% extra for settling.
| Bed (L × W × depth) | Total mix | Compost at 30% | Compost bags |
|---|---|---|---|
| 4 × 4 ft × 12 in | 16.0 cu ft (0.59 cu yd) | 4.8 cu ft | 4 |
| 3 × 6 ft × 12 in | 18.0 cu ft (0.67 cu yd) | 5.4 cu ft | 4 |
| 4 × 8 ft × 6 in | 16.0 cu ft (0.59 cu yd) | 4.8 cu ft | 4 |
| 4 × 8 ft × 8 in | 21.3 cu ft (0.79 cu yd) | 6.4 cu ft | 5 |
| 4 × 8 ft × 10 in | 26.7 cu ft (0.99 cu yd) | 8.0 cu ft | 6 |
| 4 × 8 ft × 12 in | 32.0 cu ft (1.19 cu yd) | 9.6 cu ft | 7 |
| 4 × 8 ft × 18 in | 48.0 cu ft (1.78 cu yd) | 14.4 cu ft | 10 |
| 4 × 12 ft × 12 in | 48.0 cu ft (1.78 cu yd) | 14.4 cu ft | 10 |
Need a different size or a different compost share? Use the Raised bed tab in the calculator above.
How many bags of compost make a cubic yard?
Bags are labelled in cubic feet (or litres) and a cubic yard is 27 cubic feet. Always check the volume on the bag, because two bags with the same weight can hold different amounts.
| Bag size | Bags per cu yd | Bags per m³ |
|---|---|---|
| 0.75 cu ft (21 L) | 36 | 47.1 |
| 1 cu ft (28 L) | 27 | 35.3 |
| 1.5 cu ft (42 L) | 18 | 23.5 |
| 2 cu ft (57 L) | 13.5 (buy 14) | 17.7 |
| 3 cu ft (85 L) | 9 | 11.8 |
| 40 L | 19.1 | 25 |
| 50 L | 15.3 | 20 |
Bagged vs bulk compost: which is cheaper?
Bags are convenient for small beds and containers. Bulk compost is sold by the cubic yard and almost always costs less per cubic foot, but delivery usually adds a flat fee. As a planning guide, bagged compost often works out to roughly $110 to $270 per cubic yard, while bulk compost commonly runs about $25 to $60 per cubic yard plus delivery. Prices vary a lot by region and product, so use the cost tab with your own quotes.
- Under about 6 bags: buy bags.
- 6 to 12 bags: compare bags against bulk plus delivery.
- More than about 12 to 18 bags (a cubic yard): bulk usually wins, even after delivery.
Also check how you will move it. A cubic yard of finished compost often weighs 800 to 1,200 pounds, which is too much for many car trailers when the material is wet.
How many cubic yards are in a ton of compost?
Compost is often sold by weight at some suppliers and by volume at others, so it helps to convert. Finished compost weighs roughly 800 to 1,200 pounds per cubic yard, depending mostly on moisture.
| Compost weight | Cubic yards per US ton (2,000 lb) | Weight of 1 cubic yard |
|---|---|---|
| Light / dry (800 lb per cu yd) | 2.50 | 800 lb (363 kg) |
| Typical (1,000 lb per cu yd) | 2.00 | 1,000 lb (454 kg) |
| Heavy / wet (1,200 lb per cu yd) | 1.67 | 1,200 lb (544 kg) |
The calculator shows weight in pounds, kilograms and US tons, and you can pick light, typical or heavy compost in the first tab. If your supplier quotes a weight for a cubic yard, divide 2,000 by that figure to get cubic yards per ton.
Compost vs mulch: same maths, different job
Compost is fully broken-down organic matter that feeds the soil. It is usually spread 1 to 3 inches deep or mixed in. Mulch is a surface covering such as bark or wood chips that suppresses weeds and holds moisture, normally 2 to 3 inches deep. Both are bought by the cubic yard, so the same area × depth ÷ 324 formula applies to either. Do not plant directly into pure compost; blend it with soil.
When to add compost
Spring before planting and autumn after harvest are the usual windows for garden beds, with a 2 to 3 inch layer once a year. Lawns are normally top-dressed with a thin ¼ to ½ inch layer.
Raised bed soil and compost ratios
Raised beds are filled with a blend rather than pure compost. These are the recipes the Soil mix ratio tab includes:
- Topsoil / compost / aeration (60 / 30 / 10): a budget-friendly mix. The aeration part is perlite or coarse sand.
- Mel's Mix (equal thirds): compost, peat moss or coco coir, and coarse vermiculite, from the Square Foot Gardening method. It drains well but vermiculite can be costly.
- In-ground backfill (about 25% compost): keep compost to roughly a quarter to a third of the planting-hole soil so roots reach out into the native soil.
- Container mix (1 part compost to 4 parts soil): use a lighter blend, and consider adding perlite for drainage.
Example: a 4 × 8 ft bed
A 4 × 8 ft bed is 32 sq ft. Filled 12 inches deep it holds 32 cubic feet, about 1.2 cubic yards. With 30% compost that is 9.6 cubic feet of compost (7 bags of 1.5 cu ft), and 22.4 cubic feet of everything else. Add 10% extra and order accordingly. For a bed that is already full and only needs a 2 inch top-up, you need about 5.3 cubic feet, or 4 bags of 1.5 cu ft.
Cubic yard, cubic foot, litre and m³ conversions
| 1 unit equals | Cubic feet | Cubic yards | Litres | m³ |
|---|---|---|---|---|
| 1 cubic yard | 27 | 1 | 764.6 | 0.7646 |
| 1 cubic foot | 1 | 0.0370 | 28.32 | 0.0283 |
| 1 cubic metre | 35.31 | 1.308 | 1,000 | 1 |
| 100 litres | 3.53 | 0.131 | 100 | 0.1 |
Compost calculator FAQ
How do I calculate how much compost I need?
Multiply the area in square feet by the depth in inches and divide by 324 to get cubic yards. For cubic feet, divide by 12 instead. Then add about 10% for settling and uneven ground.
How much compost do I need per square foot?
A 1 inch layer needs about 0.083 cubic feet per square foot, a 2 inch layer about 0.167, and a 3 inch layer 0.25. One cubic yard covers about 324 square feet at 1 inch, 162 at 2 inches and 108 at 3 inches.
How many bags of compost are in a cubic yard?
A cubic yard is 27 cubic feet: 36 bags of 0.75 cu ft, 27 of 1 cu ft, 18 of 1.5 cu ft, 14 of 2 cu ft (13.5 before rounding up) or 9 of 3 cu ft.
How much compost do I need for a 4x8 raised bed?
Filling it 12 inches deep takes 32 cubic feet of mix, about 1.2 cubic yards. At 30% compost that is 9.6 cubic feet, or 7 bags of 1.5 cu ft. A 2 inch top-dressing needs about 5.3 cubic feet, or 4 bags of 1.5 cu ft.
How much does a cubic yard of compost weigh?
Usually about 800 to 1,200 pounds (roughly 475 to 710 kg per cubic metre), depending mostly on moisture. Wet compost is heavier.
Is bulk compost cheaper than bagged compost?
Usually yes once you need about a cubic yard or more (12 to 18 bags). Bagged compost often equals $110 to $270 per cubic yard, while bulk is commonly $25 to $60 per cubic yard plus delivery. Use the cost tab with your own prices.
How deep should I spread compost on a lawn?
A thin layer of about ¼ to ½ inch. One cubic yard covers roughly 650 to 1,300 square feet at those depths.
What is the best ratio of compost to soil in a raised bed?
Common choices are about 60% topsoil, 30% compost and 10% perlite or coarse sand, or Mel's Mix of equal parts compost, peat moss or coco coir, and vermiculite. For planting holes in the ground, keep compost to about 25 to 30% of the backfill.
How much extra compost should I order?
Add about 10% for uneven ground and settling. For raised beds 10 to 25% extra is reasonable because fresh mix settles after watering.
How many cubic yards are in a ton of compost?
About 2 cubic yards. At 800 to 1,200 pounds per cubic yard, a 2,000 lb ton is about 1.7 to 2.5 cubic yards, and about 2.0 at 1,000 lb per cubic yard.
What is the difference between compost and mulch?
Compost is fully decomposed organic matter that feeds the soil and is usually spread 1 to 3 inches deep or mixed in. Mulch is a surface covering, often bark or wood chips, used to suppress weeds and hold moisture, and is usually spread 2 to 3 inches deep. Both are bought by the cubic yard, so the same volume formula applies.
How often should I add compost to my garden?
Most garden beds benefit from a 2 to 3 inch layer once a year, in spring before planting or in autumn after the harvest. Lawns are usually top-dressed with a thin ¼ to ½ inch layer once or twice a year.
How this calculator works
Everything runs in your browser and nothing you enter is sent anywhere. Area and depth are converted to cubic metres internally, then shown in cubic yards, cubic feet, litres and cubic metres, so US and metric results always agree. Bags are the total volume divided by the bag size on the label, rounded up. Weight uses a density you choose (about 840, 1,010 or 1,180 lb per cubic yard). Bulk orders can be rounded up to the supplier’s step size, and the break-even point is the volume where the delivery fee is paid back by the lower bulk price.
Sources and notes
- Cornell Waste Management Institute, Compost Use Estimator (volume in cubic yards = area × depth in inches × 0.0031).
- Unit conversions: 1 cubic yard = 27 cubic feet = 0.764555 m³; 1 cubic foot = 28.3168 litres.
Results are planning estimates. Compost density, bag volumes and prices vary by product and supplier, so check the label and get a quote before ordering.