Cubic Feet to Square Feet Calculator

Cubic feet to square feet calculator: volume ÷ depth

This cubic feet to square feet calculator tells you how much ground a known volume will cover. The formula is square feet = cubic feet ÷ (depth in inches ÷ 12). Enter the volume you have and the depth you want to spread it; the tool returns the coverage area rounded to the nearest square foot. It is the reverse of the usual “how much do I need” calculation.

Why depth is the missing piece

Cubic feet and square feet measure different things. A cubic foot is a box 1 ft on every side. A square foot is a flat patch 1 ft on each side with no thickness. To flatten a volume into an area, you have to say how thick the layer will be.

Picture one cubic foot of mulch. Leave it 12 inches tall and it covers 1 sq ft. Spread it 3 inches deep and it covers 4 sq ft. Spread it 1 inch deep and it covers 12 sq ft. The volume never changed; only the depth did. That is why halving the depth doubles the coverage.

Worked examples

1. Default: 50 cu ft at 4 inches

• Depth in feet: 4 ÷ 12 = 0.333 ft
• Coverage: 50 ÷ 0.333 = 150 sq ft

2. One bag of mulch: 2 cu ft at 3 inches

• Depth in feet: 3 ÷ 12 = 0.25 ft
• Coverage: 2 ÷ 0.25 = 8 sq ft per bag
• A 10 × 8 ft bed (80 sq ft) would need 80 ÷ 8 = 10 bags.

3. A half-yard scoop of topsoil: 13.5 cu ft at 4 inches

• Coverage: 13.5 ÷ 0.333 = 40.5, shown as 41 sq ft (the tool rounds to whole square feet)

Coverage reference table

Volume	1 in deep	2 in	3 in	4 in	6 in
1 cu ft	12 sq ft	6	4	3	2
2 cu ft (bag)	24	12	8	6	4
3 cu ft (bag)	36	18	12	9	6
27 cu ft (1 yd³)	324	162	108	81	54
100 cu ft	1,200	600	400	300	200

Typical depths: about 3 inches for mulch, 2 to 3 inches for decorative gravel, 4 inches for a concrete patio, and 4 to 6 inches for a gravel base.

How to measure the volume you have

• Bags: read the label. Mulch and soil bags state cubic feet, often 1.5, 2, or 3 cu ft.
• Bulk loads: suppliers sell by the cubic yard. Multiply yards by 27 to get cubic feet.
• A pile: measure the length, width, and height of the pile. A rough mound holds about half of the box that would fit around it.
• Leftover concrete: an 80-lb bag mixes to about 0.6 cu ft.

Checking whether you have enough

The most useful way to use this calculator is as a check before you spread. Measure the area you want to cover with length × width. Then run your volume through the calculator at the depth you want. If the coverage area is smaller than the bed, you are short.

For example, 6 bags of 2 cu ft mulch is 12 cu ft. At 3 inches that covers 48 sq ft. A 10 × 6 ft bed is 60 sq ft, so you would need 60 ÷ 8 = 7.5, or 8 bags.

Common mistakes

• Entering depth in feet. Typing 0.25 for a 3 inch layer gives a result 12 times too big. Use inches.
• Forgetting settling. Mulch and loose soil settle. Spread at the loose depth you want plus a little, or expect less coverage after rain.
• Mixing up yards and feet. A “yard” of mulch is 27 cu ft, not 3.
• Ignoring compaction. Gravel that will be compacted covers less area at the finished depth than this pure geometry shows.

Related calculators

To go the other way, from area and depth to volume, use the cubic feet calculator or the square feet to cubic yards calculator. For bags and bulk mulch, try the mulch calculator.

This is a pure geometry calculation. Measure the real space before ordering material.