Concrete Sidewalk Calculator
A concrete sidewalk calculator finds cubic yards as length × width × (thickness ÷ 12) ÷ 27. A 30 ft walk, 4 ft wide and 4 in thick, needs 1.48 yd³ of concrete.
How much concrete do I need for a sidewalk?
A concrete sidewalk calculator multiplies the walk’s length × width × thickness, then divides by 27 to get cubic yards: (length × width × thickness in inches ÷ 12) ÷ 27. A 30 ft walk, 4 ft wide and 4 in thick, is 40 cubic feet, or 1.48 cubic yards. At $150 a yard that is $222.22, and with 10% extra the order becomes 1.63 yd³ and $244.44.
A walkway is long and thin, so small changes in thickness move the total a lot. Going from 4 in to 5 in adds 25% more concrete along the whole run. Measure the forms after they are set and staked, not before.
The formula in plain words
- Thickness in feet = slab thickness in inches ÷ 12.
- Cubic feet = length × width × thickness in feet.
- Cubic yards = cubic feet ÷ 27.
- With waste = × 1.10 when the waste box is ticked, to cover a low subgrade and spillage.
- Cost = cubic yards × price per yard.
Worked examples
- Front walk: 30 × 4 ft, 4 in thick (calculator defaults)
- Thickness: 4 ÷ 12 = 0.333 ft
- Volume: 30 × 4 × 0.333 = 40 ft³
- 1.48 yd³, $222.22 at $150
- With 10% waste: 1.63 yd³, $244.44
- Side walk that crosses the driveway: 50 ft total, 4 ft wide
Forty feet is ordinary walk at 4 in. Ten feet crosses the driveway, so it is thickened to 6 in. Run the two sections separately.
- Walk section: 40 × 4 × (4 ÷ 12) = 53.3 ft³ = 1.98 yd³
- Driveway crossing: 10 × 4 × (6 ÷ 12) = 20 ft³ = 0.74 yd³
- Total: 1.98 + 0.74 = 2.72 yd³, or 2.99 yd³ with 10% waste
Had the whole 50 ft been poured at 4 in, it would be 2.47 yd³. The thicker crossing adds about a quarter of a yard.
Cubic yards per 10 ft of sidewalk
| Width × thickness | Yd³ per 10 ft | Ft³ per 10 ft |
|---|---|---|
| 3 ft × 4 in | 0.370 | 10.0 |
| 4 ft × 4 in | 0.494 | 13.3 |
| 5 ft × 4 in | 0.617 | 16.7 |
| 4 ft × 5 in | 0.617 | 16.7 |
| 4 ft × 6 in | 0.741 | 20.0 |
| 5 ft × 6 in | 0.926 | 25.0 |
Multiply the per-10 ft figure by your length ÷ 10. A 70 ft, 4 ft × 4 in walk is 7 × 0.494 = 3.46 yd³ before waste.
How to measure your walkway
- Length: pull a tape down the center of the planned walk. On curves, follow the curve with the tape or split it into short straight pieces.
- Width: measure inside the forms. Common residential widths run 3 to 4 ft for a side path and 4 to 5 ft for a main entry.
- Thickness: measure from the compacted base up to the top of the forms at several points. A low spot in the base is extra concrete.
- Steps and landings: a stoop or landing at the door is a separate box. Measure it on its own.
Common mistakes
- Pouring straight on soft soil. Most walks sit on a few inches of compacted gravel. Price it with the gravel base calculator, and remember a thinner base means a thicker slab if the forms stay put.
- Ignoring the driveway crossing. A 4 in walk under car tires is a common place for cracking.
- Forgetting the edges. Thickened edges or a curb along the walk add volume. Treat them as extra sections.
- Ordering exactly the net volume. A short truck is expensive. The 10% buffer is cheap insurance.
Pricing and mixing
For a full installed price including labor, use the concrete sidewalk cost calculator. To turn the yardage into 60 or 80 lb bags for a small path, see the concrete bag calculator. For other slab shapes, the general concrete calculator covers squares, circles, and steps.
Frequently asked questions
What should I enter for length and width on a walkway?
Length is the walk's total run in feet, measured down its center. Width is the poured concrete across, not counting edging. A 30 ft walk that is 4 ft wide is 120 sq ft. If the width changes, split it into sections with one width each and add the cubic yards.
How thick does a sidewalk need to be?
4 in is the usual thickness for a walk that carries only foot traffic. Where a car or truck can cross it, such as at a driveway, many builders thicken that section to 5 to 6 in. A 10 ft long, 4 ft wide crossing at 6 in takes 0.74 yd³, half again as much as the same length at 4 in.
Do sidewalks need control joints?
Yes. A common rule is to space joints about as far apart as the walk is wide, so roughly every 4 ft on a 4 ft walk, and cut them about a quarter of the slab thickness deep. Joints don't change the concrete volume; they give shrinkage cracks a straight place to form.
Does municipal code require a specific sidewalk slope or width?
Public walks often must meet accessibility rules. US ADA standards call for an accessible route at least 36 in clear and a cross slope no steeper than 1:48 (about 2%). Many cities require more width and their own details for walks in the right-of-way, so check with the local public works or building department.
How many bags of concrete is a sidewalk?
An 80 lb bag yields about 0.6 cu ft, so one cubic yard takes 45 bags. The default 30 × 4 ft walk at 4 in is 40 cu ft, or about 67 bags. That is a lot of hand mixing, so many people order ready-mix or a short-load truck past about 1 yd³.
Estimates only. Verify quantities with your supplier before purchasing.