Concrete Square Foot
Calculator — Slab Area Tool

Multiply length by width in feet to get square footage. A 20x10 ft slab is 200 square feet. To find cubic yards of concrete needed, multiply area by thickness in feet, then divide by 27.

A 10x10 ft slab (100 sq ft) at 4 inches thick needs about 1.23 cubic yards of concrete. Calculation: 100 x 0.333 / 27 = 1.23 cubic yards. Order 10% extra for spillage.

Measure driveway length and width, multiply for area, then calculate volume based on 4-6 inch thickness. A 40x12 ft driveway (480 sq ft) at 5 inches thick needs about 7.4 cubic yards.

Concrete costs $4-8 per square foot for a standard 4-inch slab including materials and labor. Decorative concrete (stamped, stained) costs $8-18 per square foot.

Standard residential slabs are 4 inches thick. Driveways should be 5-6 inches. Garage floors and heavy-load areas need 6 inches or more. Thicker slabs use more concrete but last longer.

For a 4-inch thick slab covering 100 sq ft, you need approximately 34 bags (80 lb each). Each 80 lb bag makes about 0.6 cubic feet. Total volume needed: 100 x 0.333 = 33.3 cubic feet.