Construction & DIY

Mulch & Gravel Calculator

What this does

Convert bed area and depth into cubic yards of mulch or gravel, plus 2-cu-ft bag counts and an estimated gravel tonnage.

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Calculator inputs

How to use it

Using the mulch & gravel calculator

  1. 01

    Measure the bed

    Multiply length × width for each planting bed and add them together.

  2. 02

    Pick a depth

    Mulch works best at 2–3 inches (never piled on trunks); gravel paths want 3–4 inches over fabric.

  3. 03

    Compare bags vs bulk

    Past roughly 40–50 bags, delivered loose material by the cubic yard is usually cheaper and faster to spread.

Good to know

Where the 324 comes from

One cubic yard covers 324 sq ft at one inch deep (27 ft³ × 12). Dividing area × inches by 324 collapses the unit conversion into one step; the landscape industry’s favorite constant.

Depth discipline

More mulch is not better. Piles deeper than 4 inches suffocate roots, invite rodents and mold, and shed water away from plants. Two inches refreshes color; three handles weed suppression in most climates.

Bulk vs bagged economics

Bagged mulch is convenient and clean to haul but costs roughly double per cubic yard versus bulk delivery. Gravel adds another wrinkle: it is sold by weight, so the tons row is what your quarry will actually quote you.

How it's calculated

The math behind this calculator

yd³ = Area(sq ft) × Depth(in) ÷ 324 Bags = yd³ × 27 ÷ 2 Tons ≈ yd³ × 1.35

Landscape material volume equals area times depth. With depth in inches and area in square feet, dividing by 324 converts straight to cubic yards. Bags of mulch typically hold 2 cubic feet (27 ft³ per yard), and gravel tonnage assumes a common ~1.35 tons per cubic yard bulk density.

Assumptions & limitations

  • Even spread depth across the measured area.
  • Gravel density ≈1.35 tons/yd³; river rock runs lighter, crushed stone heavier.
  • Bagged mulch assumed at 2.0 cu ft per bag; check your brand.

Worked example

Spreading mulch 3 inches deep over 500 sq ft needs about 4.63 cubic yards; roughly 63 of the 2-cu-ft bags, or about 6.25 tons if you order gravel by the truckload.

FAQ

Frequently asked questions

How deep should mulch be?
2–3 inches is the sweet spot for beds. Keep it pulled back 2–3 inches from tree trunks and stems to prevent rot.
How much does a cubic yard of gravel weigh?
Commonly 1.3–1.5 tons depending on stone. This calculator assumes ~1.35 tons/yd³, so treat the tonnage as an estimate.
Does gravel settle?
Yes; uncompacted gravel drops noticeably after the first season. Order 10–15% extra or plan a top-up year.
Is rubber mulch calculated differently?
Volume math is identical; only bag sizes differ, so adjust the bag count to your product’s stated cubic feet.

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