Square Feet to Cubic Yards Converter

Square feet cover a surface. Cubic yards fill a volume. To get from one to the other you have to add depth, because a patio slab and a driveway can have the same square footage and still need wildly different amounts of concrete. Tell this converter your area and how thick you're pouring or spreading, and it returns cubic yards, the unit concrete plants and bulk suppliers actually sell in.

Why you can't skip the depth

Area is two dimensions: length times width. Volume is three: length, width, and depth. A 400 square foot slab poured 4 inches thick is a completely different order than the same 400 square feet poured 6 inches thick. One is about 4.9 cubic yards, the other about 7.4. Same footprint, 50 percent more material.

So any honest square feet to cubic yards calculator asks for a thickness. If a page hands you a straight conversion with no depth field, walk away.

The formula

Cubic yards = (area in square feet × depth in feet) ÷ 27

Two steps, one constant to explain.

First, get everything into feet. Your area is already in square feet. Your depth is almost always given in inches, so divide by 12 to turn it into feet. Four inches is 4 ÷ 12 = 0.333 ft.

Multiply area by depth and you have cubic feet, the volume. Then divide by 27 to convert cubic feet to cubic yards.

Where the 27 comes from

A yard is 3 feet. A cubic yard is a cube that's 3 feet on every side: 3 feet long, 3 feet wide, 3 feet deep. Multiply those out and you get 3 × 3 × 3 = 27 cubic feet in a single cubic yard. That's the whole reason the number shows up. You compute the volume in cubic feet, then divide by 27 to express it in the bigger unit that dump trucks and ready mix drivers use.

Cubic feet vs cubic yards, and why the distinction bites people

These two units trip up more orders than any other part of the job. Bagged material lists cubic feet on the sack. Bulk material gets sold and delivered by the cubic yard. They're 27 apart, and mixing them up is either a wildly short order or a driveway buried in mulch.

A quick gut check: one cubic yard is 27 cubic feet, which is roughly what fits in the bed of a standard full size pickup filled level to the rails, and it weighs enough that most half ton trucks shouldn't haul a full yard of wet soil or gravel at once. If your math spits out a number that sounds like "40 cubic yards" for a small backyard, you almost certainly forgot to divide by 27 and you're staring at cubic feet.

When you're comparing bag prices to bulk, convert everything to the same unit first. A 2 cubic foot bag of mulch means you need 13.5 bags to equal one cubic yard (27 ÷ 2 = 13.5). Bulk almost always wins on price once you're past a yard or two, which is why landscapers order loose.

Depth reference table

Cubic yards needed per 100 square feet, at common depths. Multiply by your actual area in hundreds of square feet.

Depth	Depth in feet	Cubic yards per 100 sq ft	Typical use
1 in	0.083	0.31	Top dressing, thin overlay
2 in	0.167	0.62	Mulch refresh, sand base
3 in	0.250	0.93	Fresh mulch, gravel path
4 in	0.333	1.23	Standard slab, patio, walkway
5 in	0.417	1.54	Heavier slab
6 in	0.500	1.85	Driveway, garage, load bearing slab
8 in	0.667	2.47	Deep gravel base, heavy footing
12 in	1.000	3.70	Raised bed fill, deep base

Example using the table: a 300 square foot patio at 4 inches is 3 × 1.23 = 3.7 cubic yards before waste.

Worked example 1: a concrete patio

You're pouring a 12 foot by 16 foot patio, 4 inches thick, the standard for a surface that only sees foot traffic and patio furniture.

Area: 12 × 16 = 192 square feet.
Depth in feet: 4 ÷ 12 = 0.333 ft.
Volume in cubic feet: 192 × 0.333 = 63.9 cubic feet.
Cubic yards: 63.9 ÷ 27 = 2.37 cubic yards.

Round up when you order. Concrete waits for no one, and you can't run back to the plant mid pour. Most crews add roughly 10 percent for spillage, uneven subgrade, and the forms bulging a little, which takes this job to about 2.6 cubic yards. Order 2.75 or 3 yards so you're not scraping the truck clean and coming up a wheelbarrow short. In a TractorByNet forum thread on pouring a cement slab, the practical advice runs the same way: do the math, then order a bit extra, because a short load means a cold joint or a second delivery fee.

If you'd rather buy bags for a small pour, remember an 80 lb bag of concrete mix yields about 0.6 cubic feet once mixed, per the manufacturer data sheets (confirmed here). This patio's 63.9 cubic feet would take about 107 bags, which is exactly why anything past a yard goes to ready mix. Our concrete calculator breaks bags and yards down side by side.

Worked example 2: a mulch bed

You've got a curved front bed that measures out to roughly 250 square feet, and you want 3 inches of hardwood mulch for weed suppression.

Area: 250 square feet.
Depth in feet: 3 ÷ 12 = 0.25 ft.
Volume in cubic feet: 250 × 0.25 = 62.5 cubic feet.
Cubic yards: 62.5 ÷ 27 = 2.31 cubic yards.

Mulch is forgiving, so you don't need a strict waste factor. Round to 2.5 cubic yards and any extra goes on the pile for next time. Buying this as 2 cubic foot bags instead would mean about 32 bags, which is a lot of plastic and usually more money than a bulk yard delivered. Two to three inches is the depth most landscapers repeat, deep enough to block light to weed seeds without smothering roots, and it lines up with the coverage guidance in the Inch Calculator mulch tool.

Worked example 3: topsoil fill for a low spot

You're leveling a settled area of yard that's about 200 square feet, and it needs an average of 5 inches of screened topsoil to bring it up to grade.

Area: 200 square feet.
Depth in feet: 5 ÷ 12 = 0.417 ft.
Volume in cubic feet: 200 × 0.417 = 83.4 cubic feet.
Cubic yards: 83.4 ÷ 27 = 3.09 cubic yards.

Order about 3.25 to 3.5 yards. Fresh soil settles and compacts after the first few rains, so a little cushion keeps you from needing a second delivery to top it off. If you're prepping for new sod or seed on top, plan the final couple of inches as the actual growing layer and check the lawn calculator for seed and sod coverage once the grading is done.

Handling sloped or uneven depth

The formula assumes one flat depth everywhere. Real ground rarely cooperates. A bed that's 2 inches deep at the high side and 6 inches at the low side does not take the 6 inch figure, and it does not take the 2 inch figure. It takes the average.

The quick method: measure the depth at several spots across the area, add them up, and divide by how many readings you took. For that bed, (2 + 6) ÷ 2 = 4 inches average, so you run the whole calculation at 4 inches. For a driveway base that dips in the middle, take five or six readings along the run and average those instead of eyeballing a single number.

This averaging trick works because volume adds up piece by piece, and the average depth times the full area gives the same total as summing every little section. Just be honest with your readings. If most of the area is deep and only a corner is shallow, weight your samples toward where the material actually goes so the average reflects reality.

For an odd shaped space, nail the area first by breaking it into rectangles with the how to calculate square footage guide, then apply one averaged depth to the total.

Common mistakes

Leaving depth in inches. Plugging 4 into the formula instead of 0.333 throws the answer off by a factor of 12. Convert inches to feet first, every time.

Forgetting to divide by 27. Skip it and you've ordered cubic feet's worth of trucks. That's a 27 times overshoot. This is the single most common error people make going from square feet to cubic yards.

Ordering the exact number. Subgrade is never perfectly level, forms flex, and some material sticks in the chute or the wheelbarrow. Add about 10 percent for concrete and don't sweat the rounding on mulch, where a little extra just goes on the pile.

Confusing bagged and bulk units. Bags list cubic feet. Trucks and yards deliver cubic yards. Thirteen and a half bags of 2 cubic foot mulch is one cubic yard, minus the packaging premium.

Using peak depth on uneven ground. If the depth varies, average your readings instead of ordering for the deepest spot. Otherwise you'll badly over order.

Frequently asked questions

How do I calculate cubic yards from square feet?

Multiply the area in square feet by the depth in feet, then divide by 27. For a 200 square foot area at 4 inches deep, that's 200 × 0.333 ÷ 27 = 2.47 cubic yards. The depth is required; there's no conversion without it.

Why do you divide by 27?

Because a cubic yard is 3 feet by 3 feet by 3 feet, which equals 27 cubic feet. You first find the volume in cubic feet, then divide by 27 to express it in cubic yards, the unit bulk suppliers use.

How do I convert cubic feet to square feet?

Divide the cubic feet by the depth in feet. Volume divided by depth gives you back the surface area. For example, 100 cubic feet spread 0.5 feet (6 inches) deep covers 200 square feet.

How thick should I spread mulch or pour concrete?

Mulch goes down 2 to 3 inches for weed control. Concrete slabs for patios and walkways are typically 4 inches; driveways and load bearing slabs are usually 6 inches.

How many cubic yards is a 10 by 10 slab at 4 inches?

About 1.23 cubic yards before waste. That's 100 square feet times 0.333 feet of depth, divided by 27. Order around 1.5 yards to cover spillage and uneven ground.

How many bags of concrete are in a cubic yard?

An 80 lb bag yields about 0.6 cubic feet, so a cubic yard (27 cubic feet) takes about 45 bags. A 60 lb bag yields about 0.45 cubic feet, needing roughly 60 bags. Past a yard or so, ready mix delivery almost always beats mixing bags by hand.

What if my depth isn't even across the whole area?

Take depth readings at several spots, add them, and divide by the number of readings to get an average. Run the formula with that average depth against the full area. This gives the same total volume as adding up every small section separately.

Does square footage alone tell me the cubic yards?

No. Square footage is a flat area with no thickness, so it can't fix a volume. You always need the depth. Two projects with identical square footage need different cubic yards whenever their depths differ.

For any other shape or a whole project at once, start from the main square footage calculator.

Square Feet to Cubic Yards Converter