Mulch Calculator

How to Use This Mulch Calculator

Select shape: Rectangular bed or Circular area
Enter the dimensions of your garden bed
Choose depth — 2–3 inches is most common for weed control and moisture
Select bag size (2 cu ft is the standard retail bag)
Optionally enter price per bag to see estimated cost
Click Calculate Mulch to see cubic yards and bags needed

Common Mulch Examples (3" Depth, 10% Extra, 2 ft³ Bags)

Quick reference for popular bed sizes. Re-calculate with your exact dimensions and bag size.

Bed Size	Volume	Bags (2 ft³)
4 × 10 ft	~0.41 yd³	6 bags
8 × 20 ft	~1.63 yd³	23 bags
10 × 30 ft	~3.06 yd³	42 bags
Circle 10 ft diameter	~0.80 yd³	11 bags

Figures include 10% extra. Bulk delivery is often cheaper above ~1 cubic yard.

Recommended Mulch Depth

Purpose	Recommended Depth
Weed control & moisture	2 – 3 inches
New beds / heavy weeds	3 – 4 inches
Around trees & shrubs	2 – 3 inches
Decorative only	1.5 – 2 inches
Play areas (wood chips)	6 – 12 inches

Bag Coverage Reference

Bag Size	Coverage at 2" depth	Coverage at 3" depth
1.5 cu ft	~9 sq ft	~6 sq ft
2 cu ft	~12 sq ft	~8 sq ft
3 cu ft	~18 sq ft	~12 sq ft

Formulas Used

Rectangular: Volume = Length × Width × Depth

Circular: Volume = π × (Diameter ÷ 2)² × Depth

Cubic Yards = Cubic Feet ÷ 27

Number of Bags = Total Cubic Feet ÷ Bag Size (rounded up)

A small waste factor (5–10%) is recommended so you do not run short.

How Much Mulch Do I Need?

Mulch improves soil moisture, suppresses weeds, and gives beds a finished look. Ordering the right amount avoids leftover bags or a second trip to the store.

Garden Bed Mulch

Most flower and shrub beds need 2–3 inches of mulch. Measure the length and width of each bed, then use this calculator. For irregular shapes, break the area into rectangles or circles and add the results.

Around Trees

Keep mulch 2–3 inches deep in a wide circle around the tree, but pull it a few inches away from the trunk to prevent rot and pest problems. Avoid “mulch volcanoes.”

Bags vs Bulk

Bags – convenient for small beds and easy to carry
Bulk (cubic yards) – cheaper for large areas and better for the environment

Tips for Applying Mulch

Weed first — remove existing weeds before mulching.
Water the soil if it is dry, then apply mulch.
Keep mulch off stems and trunks to prevent rot.
Replenish yearly — organic mulch breaks down and feeds the soil.
Don’t overdo it — more than 4 inches can block water and air.

Frequently Asked Questions

How much mulch do I need?

Measure the length and width of your bed, decide on depth (usually 2–3 inches), then multiply length × width × depth (in feet) and divide by 27 for cubic yards. This calculator also shows how many bags you need.

How many bags of mulch equal a cubic yard?

A cubic yard is 27 cubic feet. With 2 cu ft bags you need about 14 bags (rounded up). With 3 cu ft bags you need 9 bags per cubic yard.

What is the best depth for mulch?

For most garden beds, 2–3 inches is ideal. Use 3–4 inches for new beds or heavy weed pressure. Keep mulch 2–3 inches deep around trees and shrubs, and never pile it against trunks.

Should I buy mulch by the bag or by the yard?

For small beds (under about 1 cubic yard), bags are convenient. For larger areas, bulk mulch delivered by the cubic yard is usually cheaper and creates less plastic waste.

How often should I replace mulch?

Most organic mulches break down in 1–2 years. Refresh with 1–2 inches each spring. Inorganic mulches (rubber, stone) last much longer but do not improve the soil.

Can I put new mulch on top of old mulch?

Yes. Rake the old mulch to loosen it, then add a fresh 1–2 inch layer. Avoid creating a total layer thicker than 4 inches, which can smother roots and block water.

How many square feet does a 2 cu ft bag cover?

At 2 inches deep a 2 cu ft bag covers about 12 sq ft. At 3 inches deep it covers about 8 sq ft.

Related measurements

Base rock under beds: gravel calculator. Bed area: square footage calculator. Borders: fence calculator. Browse all construction calculators.