Concrete Pad Cubic Yard Calculator

This calculator works out the volume of concrete needed for a rectangular pad in cubic yards. You enter the pad’s length, width, and depth (in feet and inches), and it returns the cubic yards of concrete required, along with the equivalent cubic feet and cubic meters. The first result is the cubic yards, which is the standard unit for ordering ready-mix concrete.

Formula

The volume of a rectangular slab is length × width × thickness. To get cubic yards, all measurements must be in yards, or you convert from feet and inches:

V (cu yd) = (L × W × D) / 27

• L = length of the pad in feet
• W = width of the pad in feet
• D = depth (thickness) of the pad in inches (converted to feet by dividing by 12)
• 27 = number of cubic feet in one cubic yard (3 ft × 3 ft × 3 ft)

If you measure in meters, the volume in cubic meters is simply L × W × D (all in meters). To convert cubic meters to cubic yards, multiply by 1.30795.

Worked Example

Using the calculator’s default values: a pad 10 ft long, 8 ft wide, and 4 inches deep.

1. Convert depth to feet: 4 in ÷ 12 = 0.3333 ft
2. Calculate volume in cubic feet: 10 × 8 × 0.3333 = 26.6664 cu ft
3. Convert to cubic yards: 26.6664 ÷ 27 = 0.9876 cu yd

Rounded to two decimals, the calculator shows 0.99 cubic yards. This matches the first output exactly.

Why Order in Cubic Yards?

Ready-mix concrete is sold by the cubic yard in the United States and Canada. A cubic yard is a cube 3 feet on each side—about 27 cubic feet. When you call a batch plant, you order in whole or half yards (e.g., 1.5 yd³), so knowing your exact volume helps you avoid over-ordering (wasted money) or under-ordering (a cold joint where new concrete meets already-set concrete).

For small pads like a shed base or a small patio, many DIYers mix their own bags. A 60-lb bag of concrete mix yields about 0.45 cubic feet; an 80-lb bag yields about 0.6 cubic feet. Divide your cubic feet total by that number to estimate bags.

How to Measure a Pad Correctly

Measure the outside dimensions of the form you’ve built. Use a tape measure and take three measurements along each side if the ground is uneven; use the average. For depth, measure from the top of the form to the ground at several points—forms often sit higher in one corner.

• For a slab on grade, depth is the thickness of the concrete (commonly 4 in for patios, 6 in for driveways).
• If you have a footing or thickened edge, calculate that volume separately and add it.
• Always round up to the nearest quarter yard when ordering.

Common Mistakes and How to Avoid Them

The biggest error is mixing units. If you measure length in feet but depth in inches, you must convert. Another is forgetting that a yard is 3 feet, so a cubic yard is 27 cubic feet, not 9. Also, don’t confuse cubic yards with square yards—a 10×10 ft pad at 4 inches deep is about 1.23 cubic yards, not 100.

Another frequent mistake is ignoring waste. Concrete shrinks slightly, forms may bulge, and you might spill some. Add 5–10% to your calculated volume for waste. For a 1-yard pour, that means ordering 1.1 yards. Most ready-mix companies will not charge you for the extra if you don’t use it, but you’ll pay for the truck anyway.

Reading the Calculator Results

The first output is the volume in cubic yards—the number you’ll order. The second is cubic feet, which is useful for bagged concrete. The third is cubic meters, handy if you’re working with metric plans or ordering from a supplier that uses metric. All three are derived from the same formula, so they always agree.

If your pad isn’t a simple rectangle, break it into rectangles, calculate each, and sum them. For a circular pad (e.g., a hot tub base), use the formula Ï€ × r² × depth, then convert to cubic yards.

Cost and Ordering Considerations

Concrete is priced per cubic yard, but the total cost includes delivery fees, minimum order charges, and sometimes a short-load fee if you order less than the truck’s minimum (often 3–4 yards). For a small pad, you might pay more per yard than for a large driveway. Many suppliers charge for the full minimum even if you use less, so it’s worth checking with local providers.

For a 10×8×4-inch pad (0.99 yd³), you’d likely order 1 yard. If the minimum is 3 yards, you’ll pay for 3—or consider mixing bags yourself. Bagged concrete is more expensive per cubic foot but avoids the minimum order problem.

Safety and Practical Tips

Concrete is heavy—about 4,000 lb per cubic yard. A 10×8×4-inch pad weighs roughly 4,000 lb, so plan for a strong subgrade and proper formwork. Wear gloves and eye protection when handling dry mix; wet concrete can cause chemical burns. If you’re pouring a pad that will support a structure (like a shed or hot tub), check local building codes for required thickness and reinforcement—many require a vapor barrier and wire mesh or rebar.

When pouring, have a helper and work quickly. Concrete sets in 30–45 minutes, so make sure your forms are level and your tools are ready. Use a screed board to level the surface and a float to smooth it. Cure the concrete by keeping it moist for at least 3–7 days, especially in hot weather.

Frequently Asked Questions

How many bags of concrete do I need for 1 cubic yard?

A 60-lb bag yields about 0.45 cubic feet, so you’d need 27 ÷ 0.45 = 60 bags. An 80-lb bag yields 0.6 cubic feet, so you’d need 45 bags. These are approximate; check the bag label for exact yield.

Can I use this calculator for a circular pad?

No, this calculator is for rectangular pads only. For a circle, use the formula π × r² × depth, where r is the radius in feet, then divide by 27 to get cubic yards.

What is the difference between cubic yards and square yards?

Square yards measure area (length × width), while cubic yards measure volume (length × width × depth). A 10×10 ft area is 100 square feet, but if you pour concrete 4 inches deep, the volume is 100 × (4/12) = 33.33 cubic feet, which is 1.23 cubic yards.

How much does a cubic yard of concrete weigh?

Standard concrete weighs about 4,000 pounds per cubic yard (approximately 2,400 kg per cubic meter). This can vary with the mix, but it’s a good estimate for planning support and transportation.

Should I order extra concrete for waste?

Yes, it’s standard practice to add 5–10% for waste, spillage, and uneven subgrade. For a 1-yard pour, order 1.1 yards. Many suppliers will only charge for what you use, but you’ll pay for the truck minimum anyway.

Can I pour concrete directly on dirt?

For a simple pad, you can pour on compacted gravel or soil, but it’s best to remove topsoil and compact the base. For structural pads, a gravel base of 4–6 inches is recommended to prevent cracking from soil movement.

Related

• Building Square Footage Calculator: How to Measure
• Building Square Calculator: How to Find Area
• Buco Concrete Calculator: How to Use It

in l | Length | ft | 10 | 0
in w | Width | ft | 8 | 0
in d | Depth | in | 4 | 0
out cy | Concrete volume | cu yd | (l * w * (d / 12)) / 27 | 2
out cf | Concrete volume | cu ft | l * w * (d / 12) | 2
out cm | Concrete volume | cu m | (l * w * (d / 12)) * 0.0283168 | 2