Sidewalk Concrete Calculator

1. Enter the walk length and width in feet and the thickness in inches (4 inches is typical).
2. Set the control-joint spacing, often about the walk width, to get the number of joints to cut.
3. Set the number of walks and a 5 to 10 percent waste allowance.
4. Read the result: cubic yards to order, the bag count, and how many control joints to tool or saw.

Here is what each result line means:

A sidewalk concrete calculator estimates the concrete for a walk or path and works out the control joints it needs. A sidewalk is a long, thin slab, so it is as much about the length and the joint spacing as the volume.

A walk is usually 4 inches thick and 3 to 5 feet wide, with control joints cut across it at regular spacing so that any cracking follows the joints instead of wandering across the surface. The tool sizes the concrete and counts the joints. For the mix itself, use the concrete mix calculator or the cement calculator, and for the mix water the water cement ratio calculator.

The volume is the same as any slab: length times width times thickness, divided by 27 for cubic yards. What a sidewalk adds is the control-joint count, worked out from the length and the joint spacing.

1. Multiply length by width by thickness in feet, and by the number of walks, for the cubic feet.
2. Add the waste allowance, then divide by 27 for cubic yards and by the bag yield for a bag count.
3. Divide the length by the joint spacing and round up for the sections; the joints are one fewer.

Suppose you are pouring a walk 40 feet long and 3 feet wide at 4 inches, with joints every 5 feet and 10 percent waste.

Calculation: the area is 120 square feet. Volume = 120 x 0.333 = 40 cu ft, or 1.48 cu yd. Adding 10 percent waste gives 44 cu ft, which is 1.63 cu yd, about 74 eighty-pound bags and roughly 3.3 short tons. At a joint every 5 feet the walk has 8 sections and 7 control joints.

The lesson: the walk is a small pour but a lot of joints. Cutting them at the right spacing is what keeps the finished sidewalk from cracking randomly.

Length and Width

A sidewalk is driven by its length. A few extra feet of a 3 foot walk is a surprising amount of concrete once you add the width and thickness.

Thickness at Crossings

A walk is 4 inches over most of its run, but where it crosses a driveway it is often thickened to 6 inches for the wheel loads. Split the walk and add the thicker section separately.

Sub-base and Over-excavation

A soft or uneven base soaks up concrete below grade, the main reason a real pour beats the geometry and the reason for a waste allowance.

Joint Spacing

Closer joints mean more cuts but better crack control. The spacing does not change the concrete volume, only the finishing work.

Control joints are planned weak lines, tooled or saw-cut across the walk, so that shrinkage cracks form at the joint rather than across the surface. For a sidewalk they are usually spaced about the width of the walk.

The joints do not change the volume you order, so size the concrete first, then set the spacing for the look and the crack control you want.

Most sidewalks are a small pour, so the choice is bags against a short-load ready-mix delivery. A short walk can be bagged; a long one is easier delivered.

Check the cubic yards above against this guide; the concrete cost calculator in the related tools prices a pour by the yard.

Ordering Concrete for a Walk

Size the order in cubic yards and add waste before you call the supplier. Most walks are a small pour, so a short-load fee may apply.

Planning the Joints

Work out how many control joints to cut and where, so the tools and the timing are ready on the day.

Costing a Bag Job

A short walk can be bagged. The bag count tells you how many to buy and whether hand mixing is realistic.

1. Missing the Control Joints

A walk with no control joints cracks where it likes. Plan the joints at a regular spacing; the tool counts them for you.

2. Forgetting the Driveway Crossing

Where a walk crosses a driveway it is usually thicker. Leaving that section at 4 inches under-orders and under-builds it.

3. Mixing Up Feet and Inches

Entering thickness in feet instead of inches shrinks the result twelvefold. Keep length and width in feet and thickness in inches.

4. Forgetting a Waste Allowance

An uneven base and spillage mean the exact geometry runs short. Keep 5 to 10 percent.

5. Not Adding Up a Path That Turns

A path with corners is several straight runs. Add their lengths, or work out each run and add the volumes.

The arithmetic is exact; the usefulness depends on the dimensions, the thickness and the waste allowance you enter, and the joint count assumes an even spacing.

It depends on the length, width and thickness. A 40 by 3 foot walk at 4 inches needs about 1.63 cubic yards with waste, roughly 74 eighty-pound bags. Enter your dimensions above for the exact figure.

Usually about the width of the walk, so a 3 foot walk is jointed roughly every 3 to 5 feet. A general rule keeps the spacing in feet to no more than 2 to 3 times the slab thickness in inches. Set your spacing above and the tool counts the joints.

Typically 4 inches for a residential or public walk, and 6 inches where it crosses a driveway and carries vehicles. The required thickness comes from your plans or local code; this tool estimates volume.

A short walk can be bagged. A 20 by 3 foot walk at 4 inches is about 37 eighty-pound bags with waste; a 40 foot walk about 74. Longer walks are usually ready-mix. The tool gives the count for your walk.

Concrete shrinks as it cures and will crack. Control joints are planned weak lines that make the crack form neatly at the joint instead of wandering across the surface. Cutting them at a regular spacing is what keeps a walk looking right.

About 150 pounds per cubic foot. A 40 by 3 foot, 4 inch walk weighs around 3 short tons of concrete, so the sub-base must be firm and even to carry it without settling.

Yes, a 5 to 10 percent waste allowance for an uneven sub-base and spillage. Running short mid-pour risks a cold joint, so the small margin is worth it.

No. The calculation runs entirely in your browser and nothing you enter is stored or sent anywhere.

• QUIKRETE Concrete Mix 1101 data sheet (QUIKRETE; bag yields 0.60, 0.45 and 0.30 cu ft).
• National Ready Mixed Concrete Association (NRMCA; ready-mixed concrete and ordering).
• American Cement Association (American Cement Association; concrete, cracking and joints).