Soil Calculator
Find out how much topsoil, garden soil, compost, mulch or potting mix you need for garden beds, raised beds, tree rings and lawns. Get cubic yards, bag counts, weight, and a bulk vs bagged price comparison, with settling included.
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Cubic yards = length × width × depth (ft) ÷ 27. A 4 × 8 ft raised bed filled 12 in deep needs 32 ft³. That is 1.2 yd³, or 16 bags of 2 ft³ (18 with settling). Mulching a 12 × 4 ft bed 3 in deep takes 12 ft³, or 6–7 bags.
How to use this soil calculator
- Pick what you are filling: a bed or area, one or more raised beds, a round bed or tree ring, or a known area such as a lawn.
- Enter the size and depth. Depth is in inches and is converted for you.
- Choose the material. It changes the weight (for hauling), not the volume.
- Keep 10–20% for settling. Fresh soil and compost compact noticeably after watering.
- Compare bulk vs bags with your local prices. Below about one yard, bags usually win.
How much area does a yard cover?
A cubic yard is 27 ft³, so it covers 324 ÷ depth in inches square feet. This works for soil, compost and mulch alike.
| Depth | Coverage per yd³ | Coverage per 2 ft³ bag | Typical use |
|---|---|---|---|
| ½ in | 648 sq ft | 48 sq ft | Lawn top dressing |
| 1 in | 324 sq ft | 24 sq ft | Compost top-up |
| 2 in | 162 sq ft | 12 sq ft | Light mulch |
| 3 in | 108 sq ft | 8 sq ft | Standard mulch |
| 4 in | 81 sq ft | 6 sq ft | Topsoil for new lawn |
| 6 in | 54 sq ft | 4 sq ft | New garden bed |
| 12 in | 27 sq ft | 2 sq ft | Raised bed |
Raised bed soil by size
| Bed | Volume | Cubic yards | 2 ft³ bags |
|---|---|---|---|
| 4 × 4 ft × 12 in | 16 ft³ | 0.59 | 8 |
| 3 × 6 ft × 12 in | 18 ft³ | 0.67 | 9 |
| 4 × 8 ft × 12 in | 32 ft³ | 1.19 | 16 |
| 4 × 8 ft × 18 in | 48 ft³ | 1.78 | 24 |
| 4 × 12 ft × 12 in | 48 ft³ | 1.78 | 24 |
Before settling. A common fill is about 60% topsoil, 30% compost and 10% aeration (perlite, pumice or fine bark). Deep beds over 18 in can be part-filled with logs and branches underneath (hugelkultur) to cut the soil bill. For mixes by ingredient, use the raised bed soil calculator.
How deep should soil and mulch be?
| Job | Depth |
|---|---|
| Mulch on beds | 2–3 in (not over 4 in) |
| Tree ring mulch | 2–4 in, kept 3–6 in off the trunk |
| Lawn top dressing | ¼–½ in |
| Topsoil for a new lawn | 4–6 in |
| New in-ground vegetable bed | 6–12 in of amended soil |
| Raised bed | Full height, 1 in below the rim |
Bags vs bulk, and what a yard weighs
A yard is 13.5 bags of 2 ft³, 18 bags of 1.5 ft³ or 27 bags of 1 ft³. Bulk soil and mulch are usually much cheaper per yard but carry a delivery charge, so bags tend to win below about one yard.
| Material | Approx. weight per yd³ | Pickup loads (1,500 lb) |
|---|---|---|
| Topsoil (dry) | 2,200 lb | 1.5 per yard |
| Garden soil mix | 2,000 lb | 1.3 per yard |
| Compost | 1,000 lb | 0.7 per yard |
| Wood mulch | 800 lb | Limited by bed volume, not weight |
Worked example
- Two raised beds, 8 × 4 ft, 12 in deep
- 2 × 32 = 64 ft³
- Add 10% settling
- 70.4 ft³ = 2.61 yd³
- In 2 ft³ bags
- 36 bags
- In bulk
- 2.75 yd³ delivered
All 18 soil & mulch calculators
Specialist calculators for every soil, mulch and amendment job.
Mulch
Soil & raised beds
Compost & amendments
Frequently asked questions
How do I calculate how much soil I need?
Length × width × depth in feet ÷ 27 = cubic yards. Divide depth in inches by 12 first, and add 10–20% for settling.
How much soil do I need for a 4×8 raised bed?
At 12 in deep, 32 ft³ (about 1.2 yd³). That is 16 bags of 2 ft³, about 18 with settling.
How many bags of mulch are in a yard?
13.5 bags of 2 ft³, 18 of 1.5 ft³ or 27 of 1 ft³.
How much area does a yard of mulch or soil cover?
324 sq ft at 1 in, 162 at 2 in, 108 at 3 in and 81 at 4 in.
How deep should mulch be?
2–3 in for most beds, never more than about 4 in, and kept a few inches away from stems and trunks.
How much does a yard of topsoil weigh?
About 2,200 lb dry, more when wet. Compost is about 1,000 lb and wood mulch about 800 lb per yard.
What this calculator assumes
- Volume is calculated from your dimensions, and settling is added on top. Weights are approximate dry values.
- Bulk orders are rounded up to the next quarter yard, with a 1 yd³ minimum used for the price comparison. Delivery is not included.
- Bag sizes are nominal. Some “2 ft³” mulch bags settle in the bag, so buy one extra for large jobs.