Square Feet to Cubic Yards Calculator
Turn a square-foot footprint and a depth into cubic yards of material.
Six area units, eight depth units and four volume units, solved in both directions.
Updated October 19, 2026
Introduction & Overview
Square feet describe a surface. Cubic yards describe the material that covers it. Between the two measurements sits the one people most often forget to take: the depth. This calculator joins all three, so a footprint you measured on the ground and a thickness you read off a plan turn into the volume you can actually order.
Three boxes, and any two of them are enough
- Fill in area and depth and read the volume.
- Fill in volume and depth and read the area the load will cover.
- Fill in volume and area and read how deep it spreads.
It is the tool for the person standing at the truck: a concrete slab for a patio or shed base, a raised bed that needs filling, a mulch layer around shrubs, gravel under a driveway apron, sand under pavers, or backfill behind a low wall. Bulk materials like these are usually bought by volume, and in the US that volume is quoted in cubic yards — which is exactly what the volume box shows by default.
Area
Square feet, square yards, square metres, square inches, square kilometres or square miles.
Height / depth
Millimetres up to yards, plus feet and inches, or metres and centimetres, kept as one measurement.
Volume
Cubic yards by default, and the same volume also available in cubic feet, cubic inches and cubic metres.
How to Use
Measure the footprint you are covering or filling
For a rectangular bed or slab, that is length times width. If you already know the surface area — from a plan, a survey or an earlier estimate — skip straight to the next step with that number.
Enter the area in the unit you measured it in
A plot that is 12 feet by 20 feet is 240 square feet, so the area box takes 240 with square feet selected. Nothing needs converting by hand: pick whichever unit your tape or drawing uses.
Enter the depth as the finished thickness
This is the thickness of material you expect to end up with, not the depth of the hole you dig to receive it. A 6-inch slab, a 3-inch mulch layer and a 4-foot-6-inch raised bed are three different depths, and all three go into the same box.
Read the volume in the unit your supplier sells in
Ready-mix is usually quoted in cubic yards, bagged soil and concrete in cubic feet, and metric suppliers in cubic metres. The result is the same physical volume whichever of them you read it in, so quote it in the one that appears on the order.
Or start from the volume you already have
If the delivery ticket says 10 cubic yards, type that into the volume box. With the area it is going on filled in as well, you get the depth that load will spread to — the quickest way to check an order before the truck is emptied.
Worked example: a patio slab
The patio is 180 square feet and the slab is specified at 6 inches thick. Convert the depth to feet first, then multiply, then divide by 27:
The volume box returns 3.33 cubic yards for those two entries. That is the geometric volume of the slab; a third of a yard is a repeating decimal, so the box shows a readable cut of it rather than an endless string of threes.
What you order is a separate decision: add the allowance you and your supplier agree on for a subgrade that is never perfectly level, then round up to the supplier's order step.
Calculation Method
One equation does the whole job: the volume of a layer is its footprint multiplied by its thickness.
volume = area of the footprint × thickness of the layer
Why the three boxes convert to metres, square metres and cubic metres first
Every entry is converted to its base unit once, and the multiplication happens there. That is why you can put an area in square feet next to a depth in millimetres and still get a sensible answer: the conversion is a single step, not a chain of hand conversions you have to keep track of.
Those factors are not rounded for convenience. The international foot is defined as exactly 0.3048 m, so a square foot is exactly 0.09290304 m² and a square inch exactly 0.00064516 m²; NIST Appendix B.9 lists both as exact conversion factors. A square yard therefore works out to 0.83612736 m² and a cubic yard to 0.764554857984 m³, with no digits lost on the way in or out.
Where the 27 comes from
A yard is three feet, so a cubic yard is a cube three feet on every side:
In imperial units only, the whole calculation is one line:
The 27 is exact, not a rounded industry figure. A layer one foot deep over 27 square feet is exactly one cubic yard, which is the quickest sanity check you can do in your head before trusting any result.
The same statement, rearranged
Solving one equation for either of its inputs is what makes the other two directions work. Nothing extra is assumed:
Feet and inches entered as a single depth are combined before that step:
If you would rather start from length, width and height than from a footprint, the cubic feet calculator for boxes and spaces takes all three dimensions and converts the result the same way.
What One Cubic Yard Covers
Most orders start with the same question: how far will one cubic yard go? Spread thinner it covers more ground, spread thicker it covers less, and the trade is linear.
| Spread depth | One cubic yard covers | Cubic yards per 100 ft² |
|---|---|---|
| 1 in | 324 ft² | 0.31 |
| 2 in | 162 ft² | 0.62 |
| 3 in | 108 ft² | 0.93 |
| 4 in | 81 ft² | 1.23 |
| 6 in | 54 ft² | 1.85 |
| 12 in | 27 ft² | 3.70 |
The coverage column is just 324 divided by the depth in inches, because one cubic yard is 27 cubic feet and each foot of depth holds twelve inches. Check the middle row against the calculator: one cubic yard spread three inches deep covers exactly 108 square feet.
Working in metric? The same logic, with a friendlier number
- One cubic metre covers 20 m² at 5 cm, or 10 m² at 10 cm.
- One cubic metre is 1.31 cubic yards, so 3 m³ of concrete is 3.92 cubic yards.
To use the table backwards, divide the area you want to cover by the coverage figure for your depth. A 240 ft² bed at 3 inches is cubic yards.
Real-World Examples
Mulch for a shrub bed — imperial, cubic yards
A bed along the front of a house measures 20 ft by 12 ft, which is 240 ft². Three inches of mulch is enough to suppress weeds without smothering the roots.
The volume box shows 2.22 cubic yards, which is 60 cubic feet if you are buying bags. A small allowance on top is normal, because the bed edge is never a perfect rectangle.
Concrete for a small slab — metric, then back to cubic yards
A shed base is drawn as 40 m² at 75 mm thick, and the ready-mix supplier asks for cubic yards. Enter the area in square metres and the depth in millimetres:
Switch the volume unit to cubic metres and the box reads exactly 3, because 40 × 0.075 is a clean product. In cubic yards it reads 3.92 — and because ready-mix is not sold to two decimal places, the order becomes a conversation about the supplier's smallest step and the allowance for an uneven subgrade.
Checking a delivery — volume and area, solved for depth
A load of 10 cubic yards arrives for a gravel apron that measures 24 ft by 30 ft, or 720 ft². Before it is tipped, you want to know how deep it will spread.
The depth box answers 4.5 inches. If the plan called for 6 inches, this load is a quarter of the depth short — better to discover that before the truck leaves than after the gravel is on the ground.
Tips & Best Practices
Break irregular shapes into rectangles
An L-shaped bed is two rectangles: measure each one, add the two areas, and put the total in the area box. Curved beds are close enough to a rectangle that fits around them, with a little less depth assumed at the edges.
Depth is the finished thickness, and on uneven ground it is an average
Read the thickness from the specification, not from whatever the ground currently allows. For a slab on a graded site, the useful figure is the mid-thickness between the high and low points; for mulch or soil, measure the depth you want after it has settled, not the depth you tip it on at.
No waste allowance is included — decide it yourself
The volume the calculator returns is the geometric volume of the layer, and nothing else. Over-order is a judgement call: a slab needs a margin for a subgrade that is not perfectly flat, a bed needs a margin for spillage and settling, and both need rounding up to the step your supplier sells in. Ask them what margin they recommend for your job rather than guessing.
Compacted fill is not the same as the space it fills
Soil and gravel compact after placement, so a hole of a given volume takes more loose material than its measured volume. Treat the number here as the volume of the space, and check the supplier's coverage or compaction guidance before ordering a fill that will be compacted.
Mixed units are fine — don't convert by hand
A depth in inches over an area in square metres is a normal sight in a renovation, and it is a single conversion here. Hand converts are where most order-of-magnitude mistakes come from, so leave them to the calculation.
Related: pricing the job rather than just measuring it? The mulch calculator with bags, bulk volume and cost turns the same area and depth into bag counts and a price.
Limitations
- •A uniform layer over a flat footprint. Real ground dips, crowns and slopes, and a slab poured over an uneven subgrade ends up thicker in the hollows than the number you entered. The result is only as good as the area and depth you measured.
- •Volume only, never weight. The calculator does not know what the material is, and two cubic yards of dry mulch and wet sand weigh very different amounts. When the supplier sells by the ton, convert the volume with the cubic yards to tons calculator using the material density.
- •Not a design or code check. Slab thickness, subgrade preparation, reinforcement, drainage and compaction requirements come from an engineer, your local building department or the material supplier — not from a volume calculation.
- •No delivery or truck rounding. The volume is a mathematical result; how it maps to bags, pallets or partial loads depends entirely on how your supplier sells it.
- •International definitions. Conversions use the international foot of exactly 0.3048 m. Areas taken from older documents based on the U.S. survey foot differ by about four parts per million — invisible at driveway scale, worth knowing if you are working in square miles.
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