Concrete, Mulch & Topsoil Calculator
Find cubic yards, bags needed, and cost for concrete, mulch, or topsoil — for any rectangular or circular area.
How to use the concrete, mulch & topsoil calculator
- 1
Choose your material — Mulch, Topsoil, or Concrete.
- 2
Select Rectangle / Slab or Circular, then enter your area's dimensions.
- 3
Enter the depth or thickness, quantity, and a waste factor.
- 4
Your cubic yards, bag counts, and estimated cost appear instantly and update as you adjust any field.
How much material do I need? The cubic yard formula
Concrete, mulch, and topsoil are all sold by volume, and the standard unit for bulk delivery is the cubic yard. Getting from your area's dimensions to cubic yards takes three steps:
- Area = length × width (or π × radius² for a circular area)
- Volume in cubic feet = area × depth (in feet — divide inches by 12 first)
- Cubic yards = volume in cubic feet ÷ 27, since there are 27 cubic feet in one cubic yard
Worked example (mulch): A 10 ft × 10 ft garden bed at 3 inches deep has an area of 100 sq ft and a depth of 3 ÷ 12 = 0.25 ft, giving a volume of 100 × 0.25 = 25 cubic feet. Adding a 10% waste factor brings it to 27.5 cubic feet, or 27.5 ÷ 27 ≈ 1.02 cubic yards — about 19 bags of 1.5 cu ft mulch, or 14 bags of 2 cu ft mulch.
Worked example (concrete): The same 10 ft × 10 ft area poured 4 inches thick for a patio slab gives a volume of 100 × (4 ÷ 12) = 33.3 cubic feet. With a 10% waste factor, that's 36.7 cubic feet, or about 1.36 cubic yards — roughly 82 bags of 60 lb concrete mix, or 62 bags of 80 lb mix.
Coverage quick reference
| 1 cubic yard covers… | At this depth |
|---|---|
| 108 sq ft | 3 inches (typical mulch depth) |
| 162 sq ft | 2 inches |
| 81 sq ft | 4 inches (typical slab or topsoil depth) |
| 65 sq ft | 5 inches |
| 54 sq ft | 6 inches (typical driveway depth) |
| 1 cubic yard equals… | Bags needed |
|---|---|
| Mulch or topsoil (1.5 cu ft bags) | 18 bags |
| Mulch or topsoil (2 cu ft bags) | 13.5 bags |
| Concrete (60 lb bags) | 60 bags |
| Concrete (80 lb bags) | 45 bags |
Tips for estimating bulk materials accurately
Depth is the number most people get wrong, since it's easy to underestimate how much a thin layer adds up over a large area. Always measure depth in inches carefully — the difference between a 2-inch and 4-inch mulch layer doubles the material needed for the exact same footprint.
For irregularly shaped beds or slabs, break the area into rectangular or circular sections, calculate each separately using the quantity field, and let the calculator sum the total cubic yardage. This is more accurate than estimating a single average length and width for an oddly shaped space.
When ordering bulk concrete, mulch, or topsoil for delivery, most suppliers sell by the cubic yard with a minimum order size — rounding up your total slightly (via the waste factor) avoids a costly second delivery if you come up short mid-project.
Frequently asked questions
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