How do I calculate how much concrete I need for my project in NB?

The core calculation is simple: (length in feet × width in feet × thickness in feet) ÷ 27 = cubic yards. Divide by 27 because there are 27 cubic feet in one cubic yard, which is how ready-mix concrete is sold in Canada.

Convert your thickness from inches to feet before calculating: 4 inches = 0.333 feet, 5 inches = 0.417 feet, 6 inches = 0.500 feet. So a 20 × 30 foot patio at 4 inches thick is: 20 × 30 × 0.333 ÷ 27 = 7.4 cubic yards.

For irregular shapes, break the area into rectangles, triangles, or circles and calculate each section separately, then add them together. A triangle is 1/2 × base × height. A circle is 3.14159 × radius² (don't forget to convert radius to feet). An L-shaped driveway is just two rectangles added together.

For footings and walls, the same formula applies but you are dealing with a rectangular cross-section multiplied by the linear length. A 16-inch-wide by 10-inch-thick footing running 60 linear feet: (1.333 × 0.833 × 60) ÷ 27 = 2.5 cubic yards. Foundation walls add the wall height and width in the same way.

For sonotubes (cylindrical pier footings common for NB deck footings), the formula is: 3.14159 × radius² × depth ÷ 27. An 8-inch diameter sonotube (4-inch radius = 0.333 feet) poured to 5 feet depth: 3.14159 × (0.333)² × 5 ÷ 27 = 0.065 cubic yards each. Eight of these for a deck: 0.52 cubic yards — well under the short-load surcharge threshold, which means you are better off using bagged concrete for this application.

Always order 10% more than your calculated volume. This buffer covers variations in sub-base depth, minor spillage, and ensures you do not run short mid-pour. Running out of concrete during a pour is a serious problem — the seam between fresh and partially set concrete (called a cold joint) is a permanent weakness in the slab. Over-ordering by one yard costs you $190 to $240 and the leftover can always be used for a small pad, extra footing depth, or patching — but running short mid-pour can cost significantly more in repairs.

NB thickness recommendations to factor into your calculation:

• Sidewalks and walkways: 4 inches minimum


• Patios: 4 inches minimum, 5 inches preferred


• Driveways: 5 inches minimum, 6 inches for truck traffic or heavy vehicles


• Garage floors: 4 to 5 inches


• Basement floors: 4 inches minimum

Most NB ready-mix suppliers are happy to confirm your volume calculation when you call for pricing — give them the dimensions and they will calculate it for you. For projects over 3 yards, delivery pricing is per yard; for smaller orders, factor in the short-load surcharge of $75 to $150.