How to use the mulch calculator
- Choose the bed shape and enter its length and width (or diameter).
- Enter the mulch depth. Most garden beds need 2 to 3 inches; 3 to 4 inches works well for weed control.
- Read the result in cubic yards for bulk orders, or in 2 and 3 cubic foot bags for store-bought mulch.
The mulch formula
Cubic yards = length (ft) × width (ft) × depth (in) ÷ 324
The number 324 comes from 12 inches × 27 cubic feet. Example: a bed 12 ft by 6 ft, 3 inches deep: 12 × 6 × 3 ÷ 324 = 0.67 cubic yards, or 18 cubic feet. That is 9 bags of 2 cubic feet.
How much area does a yard of mulch cover?
| Depth | 1 cubic yard covers | 2 ft³ bag covers |
|---|---|---|
| 1 in | 324 ft² | 24 ft² |
| 2 in | 162 ft² | 12 ft² |
| 3 in | 108 ft² | 8 ft² |
| 4 in | 81 ft² | 6 ft² |
How deep should mulch be?
- Flower beds: 2–3 inches.
- Around trees and shrubs: 2–4 inches, kept a few inches away from the trunk.
- Weed control: 3–4 inches, ideally over landscape fabric or cardboard.
- Top-up of existing mulch: about 1 inch each year.
Too much mulch can hold excess moisture against roots and stems, so avoid going deeper than about 4 inches.
Bagged vs bulk mulch
A cubic yard equals 13.5 bags of 2 cubic feet, or 9 bags of 3 cubic feet. For beds that need more than about 2 cubic yards, bulk delivery is usually cheaper and saves a lot of plastic. For small beds and top-ups, bags are easier to handle.
Common mulch types
- Shredded hardwood: long-lasting and stays in place on slopes.
- Pine bark nuggets: attractive and slow to break down, but can float away in heavy rain.
- Cedar mulch: pleasant smell and slow to decompose.
- Dyed mulch: holds its color for a season or more.
- Rubber mulch: common in playgrounds; it does not decompose.
Other calculators
Photos: ManelTor, dankeck, Burnt Pineapple Productions, Simulina, hyunjjac32 and ArchesNPS on Flickr (public domain / CC0).
Frequently asked questions
How many bags of mulch make a yard?
One cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 cubic feet or 9 bags of 3 cubic feet.
How much mulch do I need for 100 square feet?
At 3 inches deep, 100 square feet needs about 0.93 cubic yards, or 25 cubic feet. That is about 13 bags of 2 cubic feet.
How much does a yard of mulch cover?
One cubic yard covers about 162 square feet at 2 inches deep, or 108 square feet at 3 inches deep.
How deep should mulch be?
2 to 3 inches suits most beds. Use 3 to 4 inches for weed control, and keep mulch a few inches away from tree trunks and plant stems.
Last updated: November 8, 2026