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How to calculate cubic yards from square feet

By the ExactYard team · Updated October 2026 · 5 min read

You can’t convert square feet straight to cubic yards, because square feet measure area and cubic yards measure volume. You need one more number: the depth of the material. Once you have it, the math takes about ten seconds. This guide gives you the formula, worked examples, a quick calculator and a coverage chart for gravel, mulch, soil and sand.

Quick answer
Cubic yards = (square feet × depth in inches) ÷ 324

Example: 500 sq ft at 4 inches deep = (500 × 4) ÷ 324 = 6.17 cubic yards.

Square Feet to Cubic Yards Calculator

Quick calculator

Enter your area, depth and an optional waste allowance.

Cubic yards needed6.17
With extra6.79
Cubic feet166.67

Need weight, tons or cost as well? Use the full ExactYard Gravel Calculator, or the Mulch Calculator for garden beds.

The Formula (and Why It Uses 324)

A cubic yard is 3 ft × 3 ft × 3 ft, which equals 27 cubic feet. There are 12 inches in a foot, so one cubic yard also equals 27 × 12 = 324 square feet of area, one inch deep. That is where 324 comes from.

One cubic yard equals 27 cubic feet An isometric cube measuring 3 feet on each side, which holds 27 cubic feet or 324 square feet at 1 inch deep. 3 ft 3 ft 3 ft 1 yd³ 1 cubic yard = 3 × 3 × 3 = 27 cubic feet = 27 × 12 = 324 sq ft × 1 in yd³ = sq ft × inches ÷ 324
Figure 1: One cubic yard holds 27 cubic feet, which covers 324 square feet at 1 inch deep.

If your depth is in feet instead of inches, use this version: Cubic yards = square feet × depth in feet ÷ 27. Both give the same answer.

How to Calculate Cubic Yards from Square Feet, Step by Step

  1. Find the area. Multiply length by width in feet. For a circle, use π × radius². For a triangle, use base × height ÷ 2.
  2. Choose the depth in inches (see the depth guide below).
  3. Multiply the square footage by the depth in inches.
  4. Divide by 324 to get cubic yards.
  5. Add extra for waste, settling and uneven ground. Around 5 to 10% is common, more for compacted base layers.
Worked example: garden bed. A bed is 20 ft × 15 ft = 300 sq ft and needs 3 inches of mulch. (300 × 3) ÷ 324 = 2.78 cubic yards. Adding 10% gives about 3.06 cubic yards to order.

Cubic Yards from Square Feet: Examples and Chart

AreaDepthCubic yards
100 sq ft2 in0.62
200 sq ft3 in1.85
500 sq ft4 in6.17
1,000 sq ft3 in9.26
1,000 sq ft6 in18.52

These are volumes before compaction, settling or waste.

Square feet covered by one cubic yard at each depth Bar chart: 1 inch covers 324 square feet, 2 inches 162, 3 inches 108, 4 inches 81, 6 inches 54. 1 in324 sq ft 2 in162 sq ft 3 in108 sq ft 4 in81 sq ft 6 in54 sq ft
Figure 2: Area one cubic yard covers at each depth. Deeper material covers less ground.

How Deep Should Gravel, Mulch and Soil Be?

ProjectTypical depthSq ft per cubic yard
Mulch in garden beds2 to 3 in108 to 162
Decorative gravel or paths2 to 3 in108 to 162
Topsoil for lawn repair or beds3 to 6 in54 to 108
Gravel driveway surface4 to 6 in54 to 81
Paver base4 to 6 in compacted54 to 81

These are typical planning depths. Heavy vehicles, poor soil or freeze-thaw climates often need more, so check local guidance. To turn cubic yards into tons, multiply by your material’s density. Gravel is commonly about 1.3 to 1.5 tons per cubic yard, and the gravel calculator does this for you.

Common Mistakes to Avoid

  • Mixing units. Using feet for area and depth in inches without dividing by 324 (or converting inches to feet first) gives a wrong answer.
  • Forgetting compaction. Base gravel and soil settle, so you may need 10 to 15% more.
  • Ignoring irregular shapes. Split L-shapes and curves into rectangles, circles and triangles, then add the areas.
  • Rounding down. Suppliers sell in whole or half yards, so round up.

Frequently Asked Questions

How many cubic yards are in 100 square feet?

It depends on depth. At 3 inches, 100 sq ft needs about 0.93 cubic yards. At 6 inches it needs about 1.85 cubic yards.

How do I convert square feet to cubic yards?

Multiply square feet by depth in inches, then divide by 324. If your depth is in feet, multiply square feet by depth in feet and divide by 27.

How many square feet does one cubic yard cover?

One cubic yard covers about 324 sq ft at 1 inch, 162 sq ft at 2 inches, 108 sq ft at 3 inches, 81 sq ft at 4 inches and 54 sq ft at 6 inches.

Why do I need depth to calculate cubic yards?

Square feet describe a flat surface. Cubic yards describe volume, so the calculation needs the third dimension: how thick the material will be.

How many cubic yards of mulch do I need for 1,000 square feet?

At 3 inches deep you need about 9.26 cubic yards, and at 2 inches about 6.17 cubic yards, before any extra for settling.

Should I order extra material?

Usually yes. Around 5 to 10% covers waste and uneven ground, and compacted base layers often need 10 to 15%. The right allowance depends on the material and site.

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