Mulch & Soil Calculator
Find how much mulch, topsoil, or compost a garden bed needs. Enter the area and the depth you want to spread.
Example: with Bed shape Rectangle · Bed length 20 ft · Bed width 4 ft · Depth 3 in → Cubic yards: 0.74 cu yd.
- Cubic feet20.0 cu ft
- 2 cu ft bags10
- Estimated weight370 lb
Computed by the calculator below using its default values. Change any input to see your own numbers.
Bag count assumes standard 2 cu ft bags; retail bags commonly range 1–3 cu ft, so check your product label. Weight is an estimate — moisture content and the exact material affect actual weight.
3D bed · drag to rotate
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Check it outHow deep to spread
Mulch works best at 2–3 inches to suppress weeds and hold moisture. New garden soil is often 4–6 inches. Bagged material usually comes in 2 cu ft bags, but bulk delivery by the cubic yard is cheaper once you pass roughly nine bags.
How it’s calculated
Cubic yards = area × depth ÷ 12 ÷ 27. Bags = cubic feet ÷ 2 (2 cu ft bags). Area comes from whichever shape you pick: rectangle = length × width; circle = π × (diameter ÷ 2)²; triangle = 0.5 × base × height — or enter a total area directly. Estimated weight = cubic yards × an assumed density per material (mulch ≈ 500 lb/yd³, compost ≈ 1,000 lb/yd³, topsoil ≈ 2,200 lb/yd³, gravel ≈ 2,600 lb/yd³); actual weight varies with moisture and exact product. Cost estimates simply multiply your entered price per yard or per bag by the computed quantity.
Results update as you type and are estimates, not professional advice — verify important decisions with a qualified professional.
Common mistakes
- Spreading mulch too deep, which wastes material and harms plants.
- Buying bags when bulk delivery is cheaper past ~9 bags.
Frequently asked questions
How deep should mulch be?
2–3 inches is the sweet spot. Deeper can suffocate roots; shallower lets weeds through.
Bags or bulk?
One cubic yard equals about 13–14 bags of 2 cu ft. Bulk delivery usually wins on price for larger beds.
Does material type change the amount?
Volume is the same; weight differs. Gravel and wet soil are much heavier than mulch, which matters for delivery.
How accurate is the weight and cost estimate?
Both are estimates. Weight assumes an average density per material (mulch, compost, topsoil, and gravel all pack differently, and moisture adds weight), and cost simply multiplies your entered bulk or bag price by the computed quantity — check your supplier's actual density and pricing for anything you're ordering in volume.
How do I calculate a circular or triangular bed?
Pick "Circle" or "Triangle" from the bed shape dropdown. Circle uses the diameter you enter (area = π × radius²); triangle uses base × height × 0.5. Rectangle (length × width) stays the default.