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How Much Concrete for a 6x20 Sidewalk?

A sidewalk 6 feet wide and 20 feet long is 120 square feet. Poured 4 inches thick, that is 1.48 cubic yards. How much concrete for a 6x20 sidewalk with a 10 percent allowance: about 1.63 yards.

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Step-by-step

  1. Area: 6 × 20 = 120 sq ft.
  2. Volume: 120 × (4 ÷ 12) = 40.0 cu ft.
  3. Yards: ÷ 27 = 1.48 yd³.
  4. Bags instead: 67 bags of 80 lb mix (89 of 60 lb).

Concrete by thickness

ThicknessCubic feetCubic yardsYards +10%80 lb bags60 lb bags
4 in40.01.481.636789
5 in50.01.852.0484112
6 in60.02.222.44100134

Thickness for walks

Most residential sidewalks are 4 inches thick on a compacted gravel base. Thicken any section that a car, mower or delivery cart will roll over, especially where the walk meets the drive.

Joints along the walk

Walks are usually jointed every 4 to 6 feet, often at a spacing equal to the walk width, so a 6-foot walk gets a joint about every 6 feet: roughly 2 joints over 20 feet. Square panels crack less than long, thin ones.

Truck, bags or a short load

At 1.48 yards, a ready-mix truck is usually easier than bags. Long walks are often poured in sections, so ask the plant how long the truck can wait and whether there is a short-load fee.

Slope and finish

Slope the walk a little to one side for drainage and finish it with a broom for traction. Round the edges with an edging tool so they chip less.

Questions people ask

How many yards of concrete for a 6x20 sidewalk?

About 1.48 cubic yards at 4 inches thick.

How many bags for a 6x20 sidewalk?

About 67 bags of 80 lb concrete at 4 inches.

How thick should a sidewalk be?

Four inches for foot traffic, 6 inches where vehicles cross.

How far apart should sidewalk joints be?

About every 6 feet for a 6-foot-wide walk, keeping panels close to square.

How many 80 lb bags make a cubic yard?

About 45. Each 80 lb bag yields roughly 0.6 cubic feet, and a cubic yard is 27 cubic feet.

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