About this calculator
How much concrete do you need for a sidewalk? A typical 4 × 40 ft front walk at 4 inches thick takes about 2 cubic yards (roughly 90 eighty-pound bags, so ready-mix usually wins); a shorter 3 × 20 ft garden path is about ¾ of a yard (~34 bags). A sidewalk is a long, narrow slab, so the estimate is width × length × thickness. Enter your walkway's dimensions in this concrete calculator for a sidewalk and you'll get cubic yards for ready-mix, the bag count for hand-mixed pours, and an installed-cost range to check quotes against.
How the math works
Sidewalk volume is width × length × thickness, converted to feet and divided by 27 for cubic yards. A standard walkway is 3–4 feet wide and 4 inches thick. For a path that turns, add the lengths of each straight run together. The math doesn't care about corners.
Common questions
How thick should a concrete sidewalk be?
4 inches is standard for foot traffic. Where a car may cross it, like a driveway apron, go to 6 inches, and thicken the gravel base too.
How wide should a sidewalk be?
3 feet is a comfortable single-person path; 4 feet lets two people pass. Public sidewalks typically run 4–5 feet wide.
Should I use bags or ready-mix for a sidewalk?
A small 3×8 ft garden path at 4" is about 8 cubic feet, roughly 14 eighty-pound bags, a reasonable weekend mix-by-hand job. But a full 4×20 ft walk is close to a full cubic yard (~45 bags), and a 4×40 ft walk about 2 yards. At that scale, priced ready-mix delivery usually wins.
How much concrete do I need for a sidewalk?
It depends on size, but for a 4"-thick walk: a 4×20 ft sidewalk needs about 1 cubic yard (~45 eighty-pound bags), and a 4×40 ft sidewalk about 2 cubic yards (~90 bags). A narrower 3×20 ft path is roughly ¾ of a yard. Enter your exact dimensions above for the precise count.