# How much compost do I need to buy?

Computes the compost to spread over a lawn or garden bed from the area and depth, in cubic yards, cubic feet and cubic metres, with the rate per 1,000 sq ft, the bags and the cost.

- Page: https://www.acalculator.org/construction/compost-calculator
- JSON spec: https://www.acalculator.org/construction/compost-calculator.json
- Version: 251758dd6185

## Default answer

Example with the default inputs (Area 1,000 ft², Depth of compost 1 in, Bag size 1 ft³): 1,000 ft² at 1 in deep needs 3.09 yd³ of compost.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| area | Area | The area of lawn or bed to cover with compost. |
| dep | Depth of compost | How thick a layer of compost to spread before mixing it in or leaving it on top. |
| bag | Bag size | The volume of one bag of compost. Leave empty to skip the bag count. |
| price | Price per cubic yard | The price of bulk compost per cubic yard. Leave empty to skip the cost. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| yards | Compost to order | The area × the depth. |
| feet | Cubic feet | The same volume in cubic feet. |
| metres | Cubic metres | The same volume in cubic metres. |
| rate | Cubic yards per 1,000 sq ft | The volume spread on each 1,000 square feet: the depth in feet × 1,000 ÷ 27. |
| bags | Bags | The volume ÷ the bag size, rounded up. |
| cost | Estimated cost | The volume in cubic yards × the price per cubic yard. |

## Method

Compost = area × depth; cubic yards per 1,000 sq ft = depth in feet × 1,000 ÷ 27; bags = compost ÷ bag size, rounded up.

## Assumptions

- NC State Extension suggests 1 to 2 cubic yards per 1,000 sq ft (about 0.3 to 0.65 in) worked into the top 6 to 8 inches of heavy clay or sandy soil.
- The volume is of compost as delivered, with nothing added for waste or settling.
- The cost is the bulk price per cubic yard × the cubic yards; delivery is not counted.

## Worked examples

1. area = 92.90304, dep = 0.0254, bag = 0.028317 gives feet = 2.359737, yards = 2.359737, rate = 3.08642, bags = 84. Source: NIST Handbook 44, Appendix C, General Tables of Units of Measurement (1 yd³ = 27 ft³; 1 ft = 12 in = 0.3048 m), https://www.nist.gov/pml/owm/nist-handbook-44-current-edition (retrieved 2026-10-03); NC State Extension, Extension Gardener Handbook, chapter 9 Lawns (for heavy clay or sandy soils, mix 1 to 2 cubic yards of compost per 1,000 square feet into the top 6 to 8 inches), https://content.ces.ncsu.edu/extension-gardener-handbook/9-lawns (retrieved 2026-10-03).
2. area = 18.580608, dep = 0.0508, bag = 0.042475, price = $40.00 gives yards = 0.943895, bags = 23, cost = $49.38. Source: NIST Handbook 44, Appendix C, General Tables of Units of Measurement (1 yd³ = 27 ft³; 1 ft = 12 in = 0.3048 m), https://www.nist.gov/pml/owm/nist-handbook-44-current-edition (retrieved 2026-10-03).
3. area = 10, dep = 0.05, bag = 0.04 gives metres = 0.5, bags = 13. Source: NIST Handbook 44, Appendix C, General Tables of Units of Measurement (1 yd³ = 27 ft³; 1 ft = 12 in = 0.3048 m), https://www.nist.gov/pml/owm/nist-handbook-44-current-edition (retrieved 2026-10-03).

## FAQ

### How do I work out how much compost I need?

Multiply the area by the depth, in the same units. 1,000 sq ft at 1 inch deep is 1,000 × 1/12 = 83.3 cubic feet. Divide by 27 for cubic yards: 3.09 yd³.

### How much compost should I put on a lawn or bed?

NC State Extension suggests mixing 1 to 2 cubic yards of compost per 1,000 sq ft into the top 6 to 8 inches of heavy clay or sandy soil. That is a layer about 0.3 to 0.65 inch deep before you mix it in. The calculator shows your rate in cubic yards per 1,000 sq ft to compare.

### How many bags of compost make a cubic yard?

A cubic yard is 27 cubic feet, so 27 bags of 1 cu ft, 18 bags of 1.5 cu ft, or 20 bags of 40 L (764.6 L ÷ 40 = 19.1, rounded up). Type your bag size and the calculator rounds the bags up.

### Is bulk or bagged compost cheaper?

Type the bulk price per cubic yard to see the bulk cost, then compare it with the bag count × the price of one bag. Remember that delivery adds to the bulk price.

### How do I measure an odd-shaped bed?

Split it into rectangles and circles, work out each area, and add them. A rectangle is length × width; a circle is 3.14 × radius².

### Can I use metric units?

Yes. Switch to Metric or pick the units by each box: square metres, centimetres and litres. 10 m² at 5 cm is 0.5 m³, or 500 L.

## Sources

- NC State Extension, Extension Gardener Handbook, chapter 9 Lawns (mix 1 to 2 cubic yards of compost per 1,000 square feet into the top 6 to 8 inches of heavy clay or sandy soils), retrieved 2026-10-03. https://content.ces.ncsu.edu/extension-gardener-handbook/9-lawns
- NIST Handbook 44, Appendix C, General Tables of Units of Measurement (1 yd³ = 27 ft³; 1 ft = 12 in = 0.3048 m), retrieved 2026-10-03. https://www.nist.gov/pml/owm/nist-handbook-44-current-edition