Guides & answers
All 14 guides →How to figure out how much material you need
Short answer: multiply length × width in feet by depth in inches, divide by 324 to get cubic yards, and add about 10% extra. Then compare the bag count at the store with a bulk load plus its delivery fee. Small jobs are cheaper in bags; big ones are cheaper in bulk.
The formula
Worked example: a 10 × 10 ft patio, 4 inches thick
| Step | Result |
|---|---|
| 10 × 10 × 4 ÷ 12 | 33.3 ft³ |
| +10% extra | 36.7 ft³ = 1.36 yd³ |
| 80 lb bags (36.7 ÷ 0.6) | 62 bags = $403 at $6.50 |
| Ready-mix (1.5 yd³ × $170 + $150 short load) | $405 |
At this size it's a toss-up on price, but the truck saves mixing 62 bags (almost 5,000 lb). One size smaller and bags win; one size bigger and the truck wins. That's why every BagOrBulk calculator shows both.
Why BagOrBulk
- Bags vs bulk on every result, with delivery and short-load fees, not just a volume.
- Several areas in one project: two beds and a tree ring, or a slab plus footings.
- Post holes and round pads as well as rectangles and triangles.
- Your prices: every price, density and waste allowance can be edited, and the link keeps them.
Frequently asked questions
How do I calculate cubic yards?
Multiply length (ft) by width (ft) by depth (in), divide by 12 to get cubic feet, then divide by 27. Shortcut: square feet × depth in inches ÷ 324 = cubic yards.
How many bags of concrete are in a yard?
About 45 bags of 80 lb concrete, 60 bags of 60 lb or 90 bags of 40 lb, using the manufacturers' yields of 0.6, 0.45 and 0.3 cubic feet per bag.
How much does a yard of gravel weigh?
About 1.4 tons (2,800 lb). It ranges from 1.3 to 1.5 tons depending on stone size and moisture.
How many bags of mulch are in a yard?
13.5 bags of 2 cubic feet, or 9 bags of 3 cubic feet.
When is bulk cheaper than bags?
At typical 2026 prices, bulk wins above about half a cubic yard of gravel, about 1 yard of topsoil, 1¼ yards of concrete and 5 yards of mulch. Delivery fees and local prices move these points, so enter yours.
How much extra should I buy?
About 10% for concrete, gravel and soil (spillage, compaction and settling) and 5% for mulch. The calculators add it automatically, and you can change it.
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