Mulch Calculator

How much mulch do I need? Multiply bed length × width × depth (inches ÷ 12) to get cubic feet, divide by 27 for cubic yards of bulk mulch, then divide cubic feet by your bag size and round up for bagged mulch. A 20×10 ft bed at 3 inches needs about 1.85 cubic yards — or 25 two-cubic-foot bags.

Reviewed / updated August 2026

Full walkthrough: How to Estimate Materials for Any Home Project

Your inputs

ft
ft
in

Most flower and shrub beds use about 2–3 inches

cu ft

Common retail mulch bags are 2 cubic feet

Result

Mulch to buy

1.85 cu yd

Bulk volume · or 25 bags (2 cu ft each)

Cubic yards (bulk)
1.85 cu yd
Cubic feet
50.0 cu ft
Bags (rounded up)
25

This bed needs about 1.85 cubic yards of mulch in bulk, or 25 bags at 2 cu ft each (bags rounded up).

Suggested next steps

  • At a cubic yard or more, bulk delivery is often cheaper per yard than retail bags — compare your local landscape yard.
  • Refresh mulch annually as it breaks down; top-dress rather than burying old layers too deep.
  • Use the Gravel Calculator for paths beside beds, or Grass Seed for lawn areas you’re converting.

How the mulch calculation works

  1. Cubic feet = length (ft) × width (ft) × (depth in inches ÷ 12)
  2. Cubic yards = cubic feet ÷ 27
  3. Bags = ceil(cubic feet ÷ bag cubic feet)

Depth converts from inches to feet because landscape beds are measured in inches while volume is in cubic feet and yards. Bag counts always round up so you do not short the bed. Most flower and shrub beds look and perform best at about 2–3 inches—thinner layers weed poorly, and piles much deeper than 4 inches can smother roots. Keep mulch a few inches clear of trunks and stems.

Source note: Volume math is geometric (no API). Bag sizes and coverage claims on labels can differ by brand and how loosely mulch settles — treat bag counts as a shopping estimate. Updated August 2026.

Worked example

Bed 20 × 10 ft, depth 3 inches, bags 2 cu ft:

  1. Cubic feet = 20 × 10 × (3 ÷ 12) = 50 cu ft
  2. Cubic yards = 50 ÷ 27 ≈ 1.85 cu yd
  3. Bags = ceil(50 ÷ 2) = 25 bags

Those are the default inputs on this page. At roughly 1.85 cubic yards, compare bulk delivery from a landscape yard with twenty-five retail bags—bulk often wins on price once you need a yard or more. For paths and aggregate instead of organic mulch, use the Gravel Calculator. For lawns, try the Grass Seed Calculator.

Tips and related tools

Frequently asked questions

How much mulch do I need for a 20×10 bed?

At 3 inches deep: cubic feet = 20 × 10 × (3 ÷ 12) = 50 cu ft. Cubic yards = 50 ÷ 27 ≈ 1.85 cu yd. With 2 cu ft bags you need ceil(50 ÷ 2) = 25 bags. Change depth or bag size in the calculator for your bed.

How deep should mulch be?

Most flower and shrub beds do well at about 2–3 inches. Thinner layers weed poorly; much deeper than 4 inches can smother roots. Keep mulch a few inches away from trunks and stems.

Is bulk mulch cheaper than bags?

Often yes once you need a cubic yard or more. Bags win for small beds and easy haul-home trips. Compare your local landscape yard’s price per cubic yard with retail bag totals.

What size are mulch bags?

Two cubic feet is a common retail size in the US. Some brands sell 1.5 or 3 cu ft bags — enter the size printed on the bag so the bag count is accurate.

Can I mulch over weeds?

Mulch suppresses new weeds better over clean soil or landscape fabric. Pull existing weeds first, then apply 2–3 inches so sunlight does not reach the seed bank.

Related tools

Related calculators — live tools and upcoming pages for internal linking.