Can I convert square feet to cubic feet?

Yes — but only if you know the depth or thickness. Cubic feet equals square feet times depth in feet. The default below assumes a 3-inch depth.

How do I find cubic feet of mulch from square feet?

Multiply square feet by your desired depth in feet. For 200 ft² at 3 inches deep: 200 × 0.25 = 50 ft³.

What is 100 square feet of soil 6 inches deep in cubic feet?

100 × 0.5 = 50 ft³, or about 1.85 cubic yards.

How do I size a concrete slab from square feet?

For a 4-inch slab, multiply ft² by 0.333 to get ft³, then divide by 27 for cubic yards. For a 100 ft² slab at 4 inches: 100 × 0.333 = 33.3 ft³ ÷ 27 ≈ 1.23 yd³. For a 6-inch slab use 0.5; for 8-inch use 0.667.

Square Feet to Cubic Feet Calculator — sq ft × Depth for Mulch & Concrete

How to convert square feet to cubic feet

Square feet measures area; cubic feet measures volume. To convert from area to volume, multiply by a depth (in feet). The relationship is ft³ = ft² × depth.

ft³ = ft² × depth (ft)

Worked examples

Example 1: A 200 ft² garden bed at 6 inches of soil

200 × 0.5 = 100 ft³ of soil needed.

Example 2: A 500 ft² patio at 4 inches of concrete

500 × 0.333 ≈ 166.7 ft³, or about 6.17 cubic yards.

Example 3: A 1,000 ft² yard at 2 inches of mulch

1,000 × 0.167 ≈ 166.7 ft³, or about 6.17 cubic yards.

Multiplier by depth (per ft²)	Conversion factor	Worked example
1 inch deep	× 0.083	0.083 ft³ per ft²
2 inches deep	× 0.167	0.167 ft³ per ft²
3 inches deep	× 0.25	0.25 ft³ per ft²
4 inches deep	× 0.333	0.333 ft³ per ft²
6 inches deep	× 0.5	0.5 ft³ per ft²
12 inches deep	× 1	1 ft³ per ft²

Common uses

Calculating soil for raised beds and gardens
Mulch and bark coverage planning
Concrete slab volume from floor area
Topsoil and lawn-leveling estimates

Where this conversion comes up

Square feet alone is not enough to get cubic feet — you need a depth or height. The conversion is simple multiplication once you know it.

Mulch, soil, and gravel — measure the bed in square feet, multiply by depth (in feet) for cubic feet.
Room volume for HVAC sizing — square footage from floor plans, ceiling height for the third dimension.
Concrete pads — slab area in square feet, thickness in inches.

Common mistakes to avoid

Forgetting to multiply by depth. Square feet × depth (in feet) = cubic feet. Without a depth, there is no “conversion” — they measure different things.
Using inches for depth without converting. If your depth is in inches, divide by 12 before multiplying. Otherwise your answer is 12× too large.
Mixing square feet with square inches. 1 ft² = 144 in², so a spec in square inches needs to be divided by 144 first.

Expert tips

Multiply square feet by depth (in feet) to get cubic feet.25 ft² × 0.5 ft (6 inches) = 12.5 ft³.
For mulch beds at 3 inches deep, multiply ft² by 0.25. Quick shortcut for the most common landscape job. See the mulch calculator.
For concrete slabs at 4 inches thick, multiply ft² by 0.333.Standard residential slab depth. The concrete calculator applies this.
For HVAC sizing, ft² × ceiling-height-in-feet = room volume.Use this for CFM and air-changes-per-hour calculations.
For raised garden beds, depth varies by crop. Lettuce: 6 inches (0.5 ft). Peppers: 12 inches (1 ft). Carrots: 18 inches (1.5 ft). The raised bed calculator applies the right defaults.

Frequently asked questions

Related calculators

ft³ → ft²

Convert cubic feet to square feet given a known depth or height.

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ft² → yd³

Convert square feet to cubic yards using a depth.

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Mulch

Calculate cubic feet of mulch and convert to standard 1, 1.5, and 2 ft³ bag counts.

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Concrete

Calculate cubic feet of concrete for slabs, footings, and pathways. Includes bag count and weight.

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