How Much Concrete Do I Need? (Cubic Yards & Bags)
Length × width × depth, converted to yards — plus the 10% rule that saves every pour
Ordering concrete is a two-way street with no middle lane: order too little and you're pouring a cold joint; order too much and you're paying to haul it away. Here's how to get the number right — every time.
The formula
Cubic yards = (Length ft × Width ft × Depth in ÷ 12) ÷ 27
The math is just volume (in cubic feet) divided by 27 (cubic feet per cubic yard).
The 10% rule
Always add 10% for waste, uneven forms, and spillage. A short pour mid-slab is a disaster; a half-yard extra costs less than the hassle.
Worked examples
Example 1: 10×10 patio, 4 inches deep
(10 × 10 × 4 ÷ 12) ÷ 27 = 1.23 cubic yards → order ~1.35
Example 2: 20×30 driveway, 5 inches deep
(20 × 30 × 5 ÷ 12) ÷ 27 = 9.26 cubic yards → order ~10.2
Example 3: 12×12 shed pad, 4 inches deep
(12 × 12 × 0.33) ÷ 27 = 1.76 cubic yards → order ~1.95
Mixing by hand? Here's the bag math
One 60-lb bag yields ~0.45 cubic feet
One 80-lb bag yields ~0.6 cubic feet
One cubic yard = 27 cubic feet = 45 bags of 80-lb (or 60 of 60-lb)
Quick coverage reference
| Thickness | One yard covers |
|-----------|-----------------|
| 4 inches | 81 sq ft |
| 5 inches | 65 sq ft |
| 6 inches | 54 sq ft |
Do the math in seconds
Use the free [concrete calculator](https://prybar.ai/tools/concrete-calculator) — enter length, width, and depth, and it gives you cubic yards for the truck order and the exact 60-lb and 80-lb bag counts for hand mixing. The 10% rule is built in.
The one thing that ruins pours
Not the math — the communication. Customers text "can you pour my patio next week?" and whoever answers first with a real price gets the job. That's the front end [Prybar handles for construction crews](https://prybar.ai/for-construction-contractors) — instant replies, booking, and follow-ups — while you handle the actual pour.
Bottom line: length × width × depth ÷ 27, add 10%, and order with confidence. Run it through the [calculator](https://prybar.ai/tools/concrete-calculator) first.
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