If you want to calculate cubic yards for a concrete slab, a mulch bed, a gravel driveway, or a load of topsoil, you only need one formula and about sixty seconds with a tape measure. Suppliers price and deliver bulk materials by the cubic yard, so getting this math right is the difference between one clean delivery and paying for a second truck — or finding somewhere to dump the extra. Contractors, landscapers, and DIYers all use the same formula, and this guide walks you through it step by step: the exact equation, a simple 4-step process, real project examples with numbers, bag-to-yard conversions, and the mistakes that cost homeowners the most money.
What Is a Cubic Yard?
A cubic yard — written as yd³ — is the volume of a cube that measures 3 feet long, 3 feet wide, and 3 feet tall. Multiply those three sides together (3 × 3 × 3) and you get 27 cubic feet, which is exactly what one cubic yard holds. Picture a box about the size of a large washing machine: that is roughly one cubic yard of material.
Nearly every bulk landscaping and construction material is sold this way. Concrete, topsoil, mulch, gravel, and sand are all priced and delivered by the cubic yard, which is why this single unit shows up in almost every outdoor project estimate — and why knowing how to calculate it saves real money before you ever pick up the phone to order.
One more thing worth knowing: a cubic yard is a unit of volume, not weight. The same cubic yard weighs very different amounts depending on the material — roughly 4,000 lbs for concrete, 2,800 lbs for gravel, 2,200 lbs for topsoil, and only 500–800 lbs for mulch. That matters when you are hauling material yourself, because your truck will hit its weight limit long before it runs out of space on heavy loads.
3 ft × 3 ft × 3 ft = 27 CUBIC FEET
The Cubic Yard Formula
The formula never changes, no matter what material you are buying:
Why divide by 27? Because that is the conversion from cubic feet to cubic yards. You multiply the three sides to get cubic feet, then divide by 27 — the number of cubic feet in one cubic yard — to translate the result into the unit your supplier actually sells. If you would rather skip the arithmetic, an online tool like the cubic yard calculator at Calculator Soup runs the same formula instantly. Still, knowing the math helps you sanity-check any quote before you pay for it.
Going the other way is just as easy: multiply cubic yards by 27 to get cubic feet. If a supplier quotes you 2.5 cubic yards of topsoil, that is 2.5 × 27 = 67.5 cubic feet — handy when you are comparing a bulk quote against bag labels, which always list yield in cubic feet.
If volume math is new to you, start with our plain-English guide: how do I calculate the volume.
How to Calculate Cubic Yards in 4 Steps
Grab a tape measure and work through these four steps in order. We will use a 10 ft × 10 ft area, 3 inches deep in gravel, as our running example.
Step 1 starts with accurate measurements — a tape measure is the only tool you need.
| Depth (inches) | Depth (feet) |
|---|---|
| 1″ | 0.08 |
| 2″ | 0.17 |
| 3″ | 0.25 |
| 4″ | 0.33 |
| 6″ | 0.50 |
| 12″ | 1.00 |
Cubic Yard Calculation Examples for Common Projects
- Concrete patio slab — 12 ft × 10 ft × 4 in. deep. Convert 4 inches to 0.33 ft. Then 12 × 10 × 0.33 = 39.6 cubic feet ÷ 27 = 1.47 cubic yards. Add 5–10% waste and order about 1.75 yards of ready-mix. Anything under half a yard can come from bags; above that, a ready-mix truck is cheaper.
- Mulch flower bed — 20 ft × 8 ft × 3 in. deep. 20 × 8 × 0.25 = 40 cubic feet ÷ 27 = 1.48 cubic yards — order 1.5 yards. Handy shortcut: one cubic yard of mulch covers about 108 square feet at 3 inches deep (324 ÷ depth in inches).
- Gravel driveway section — 30 ft × 10 ft × 4 in. deep. 30 × 10 × 0.33 = 100 cubic feet ÷ 27 = 3.7 cubic yards. Gravel compacts and settles after delivery, so add 10–20% and order 4 to 4.5 yards.
- Topsoil for raised beds — 8 ft × 4 ft × 12 in. deep. 8 × 4 × 1.0 = 32 cubic feet ÷ 27 = 1.19 cubic yards. Soil settles noticeably in the first season, so ordering 1.25 to 1.5 yards is the safe play.
- Round fire-pit area — 6 ft diameter × 4 in. deep. For circles, use 3.14 × radius × radius × depth (ft) ÷ 27. That is 3.14 × 3 × 3 × 0.33 = 9.3 cubic feet ÷ 27 = 0.35 cubic yards.
Gravel is sold by the cubic yard and settles after delivery — always add 10–20% extra.
If you only know the square footage of your project so far, run it through our Square Footage Calculator first, then multiply by the depth in feet and divide by 27.
How Many Bags of Concrete or Soil Equal a Cubic Yard?
Bagged material is sold by weight, but your project needs volume — so convert before you buy. Every bag lists its yield in cubic feet on the label; divide 27 by that number to get bags per yard. Standard yields:
| Bag | Yield per bag | Bags per cubic yard |
|---|---|---|
| 80-lb concrete | 0.6 cu ft | 45 |
| 60-lb concrete | 0.45 cu ft | 60 |
| 40-lb concrete | 0.3 cu ft | 90 |
| 40-lb topsoil (0.75 cu ft bags) | 0.75 cu ft | ≈36 |
| 40-lb topsoil (0.5 cu ft bags) | 0.5 cu ft | ≈54 |
The topsoil numbers vary because soil is sold by weight while volume depends on density and moisture — a damp, dense bag holds less volume than a dry, fluffy one, so always check the cubic-feet figure printed on the specific bag you are buying. Rule of thumb: if your project needs more than about half a cubic yard of concrete, ready-mix delivery is usually cheaper — and far less back-breaking — than hauling 20+ bags. For an independent double-check of the bag math, SubcontractorHub’s cubic yard calculator pairs a handy bag chart with the same volume formula.
5 Costly Mistakes When You Calculate Cubic Yards
- Mixing inches and feet. The number-one error is multiplying feet by inches without converting. Always divide the depth in inches by 12 before you multiply — a 4-inch depth entered as “4” instead of “0.33” inflates your result twelvefold.
- Forgetting depth entirely. Square feet measure area; cubic yards measure volume. A 100-square-foot patio needs very different amounts of material at 2 inches deep versus 6 inches deep, so depth is never optional in the formula.
- Skipping the ÷ 27. Multiplying length × width × depth gives cubic feet. Without dividing by 27, you will over-order by a factor of 27 — the single most expensive mistake on this list.
- Ordering the exact decimal with no waste. Spills, uneven subgrade, and settling consume 5–20% of every load. Suppliers expect you to round up; running short mid-pour — especially with concrete — costs far more than a little extra material.
- Measuring finish depth instead of dig depth. For patios and walkways, calculate using the excavated depth, including the compacted base layer, not just the visible surface. The base is material you still have to buy.
Frequently Asked Questions About Cubic Yards
Why do you divide by 27 to get cubic yards?
You divide by 27 because one cubic yard contains exactly 27 cubic feet. A yard is 3 feet, so a cubic yard is 3 ft × 3 ft × 3 ft = 27 cubic feet. Dividing your cubic-foot total by 27 converts it into cubic yards.
How many square feet will one cubic yard cover?
It depends on the depth: one cubic yard covers 324 sq ft at 1 inch deep, 162 sq ft at 2 inches, about 108 sq ft at 3 inches, 81 sq ft at 4 inches, and 54 sq ft at 6 inches. The shortcut is 324 ÷ depth in inches.
How do I calculate cubic yards from square feet?
Multiply the square footage by the depth in feet, then divide by 27. Example: 200 sq ft at 4 inches (0.33 ft) deep = 200 × 0.33 ÷ 27 = 2.44 cubic yards.
How many 80 lb bags of concrete are in a cubic yard?
45 bags. Each 80-lb bag yields about 0.6 cubic feet, and 27 ÷ 0.6 = 45. For anything over half a cubic yard, ready-mix delivery is usually the better deal.
Will one cubic yard fit in a pickup truck?
By volume, yes — one cubic yard fits in most full-size pickup beds. Weight is the real limit: a yard of topsoil weighs roughly 2,000–2,400 lbs and gravel can exceed 3,000 lbs, which pushes past many half-ton payload ratings. Check your truck’s payload sticker before loading heavy material.
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Zayn Robert is a content specialist focused on roofing, construction, and home improvement topics. He creates easy-to-understand guides that help homeowners learn about roof measurements, materials, maintenance, and repair decisions. His work combines detailed research with practical insights from roofing professionals at Zuniga Roofing Inc.