Square Feet to Cubic Yards Calculator 2026

The Formula — Square Feet to Cubic Yards

The square feet to cubic yards conversion is an area to volume calculation that requires one additional input — the depth. Square feet measure a flat surface area with no thickness. Cubic yards measure volume — a three-dimensional space. To convert between them, depth is the third dimension that completes the calculation.

Rectangle example: A 20 × 15 ft garden bed at 3 inches deep. Area = 300 sq ft. Cubic yards = 300 × 3 ÷ 324 = 2.78 yd³. Add 10%: order 3.06 cubic yards.

Circle example: A circular tree ring 10 ft diameter at 4 inches deep. Area = π × 5² = 78.5 sq ft. Cubic yards = 78.5 × 4 ÷ 324 = 0.97 yd³. Add 10%: order 1.07 cubic yards.

Triangle example: A triangular corner bed with base 12 ft and height 8 ft at 3 inches. Area = 0.5 × 12 × 8 = 48 sq ft. Cubic yards = 48 × 3 ÷ 324 = 0.44 yd³. Add 10%: order 0.49 cubic yards.

Known square footage: If you already know your area in square feet from plans or a previous measurement — enter it directly using the "Known Sq Ft" tab in the calculator above. No need to re-enter length and width separately.

Pre-Calculated Table — Common Areas

All figures include a 10 percent buffer for settling and uneven ground. Order the amounts shown — never order less than calculated.

Reverse — Cubic Yards to Square Feet Coverage

Use the reverse conversion when a supplier quotes you a volume and you need to verify it covers your project area at the required depth. The reverse formula: Cubic yards × 324 ÷ Depth (inches) = Square feet covered.

This reverse coverage table works for any material — pea gravel, crushed stone, mulch, topsoil, sand. The material type does not affect the square feet calculation, only the weight. Use the cubic yards to tons converter to get the weight after calculating the volume here.

Why Depth Is Required

Square footage and cubic yards measure completely different things. Square footage is a two-dimensional measurement — it describes a flat surface. A 100 square foot patio tells you how large the surface is but nothing about how deep the material goes. Cubic yards are three-dimensional — they describe volume. To convert from a flat area to a volume, you must add the depth as the third dimension.

A simple way to think about it: imagine a 100 sq ft sheet of paper lying flat. It has area but no volume. Now imagine lifting it into a cube — the depth is what creates the volume. One inch of depth gives you a completely different cubic volume than three inches of depth over the same area.

This is why calculators that claim to convert square feet to cubic yards with a single multiplication factor are wrong. The answer is always different depending on how deep the material is applied. The correct formula always requires both area and depth.

Depth Guide by Project Type

For pea gravel specifically, the sizes guide explains which grade to use at each depth for every project type. The gravel calculator handles project-specific depth recommendations automatically for each material type.

Square Feet to Bags

Once you have the cubic yards from the formula above, convert to 50-lb bags as follows: Cubic yards × 27 ÷ 0.5 = number of 50-lb bags. Each standard 50-lb bag holds 0.5 cubic feet. One cubic yard equals 54 standard bags.

Above 3 cubic yards, bulk delivery is almost always cheaper than bags. The coverage calculator gives exact bag count and cost comparison for any area and depth.

Related Calculators