Concrete Sidewalk Calculator

How to use this calculator

1. Enter the length and width of the walk. Width can go in feet or inches, since sidewalk standards are written in both.
2. Pick a thickness. Four inches is the standard almost everywhere.
3. Add a waste allowance. A narrow walk poured against a hand-dug subgrade belongs at the top of the range.
4. If the walk crosses a driveway, open the optional panel and enter how many feet of it. That section gets priced at 6 inches.
5. Read the yards to order, then the joint layout, the width check and the form lumber underneath it.

The result gives the number of control joints and the panel length they produce, so you can mark the walk out before you pour rather than after.

The formula

A sidewalk is a long, thin slab, so the volume is the same arithmetic as any other flatwork. Convert the thickness to feet first.

Cubic yards = (Length ft × Width ft × Thickness ft) ÷ 27

Worked example. A 40 foot walk, 4 feet wide, 4 inches thick. Four inches is 0.333 ft, so 40 × 4 × 0.333 = 53.3 cubic feet, which is 1.98 cubic yards. Add 10 percent and order about 2.2 yards.

That is under the short-load threshold at most suppliers, which is worth knowing before you call: published thresholds run from 3 to 7 cubic yards, and the fee is usually a flat $200 to $300 rather than a per-yard charge. Ready-mix delivery covers what those fees actually look like, and for a walk this size it is worth pricing bags against a truck.

How wide, and which rule applies to you

This is the question people get wrong most often, because there are two different accessibility numbers and they belong to two different places.

In the public right of way, the number is 48 inches. The Access Board's 2023 PROWAG final rule, section R302.2, requires that "the continuous clear width of pedestrian access routes shall be 48 inches (1220 mm) minimum, exclusive of the width of any curb." On medians and pedestrian refuge islands R302.2.1 raises it to 60 inches.

On private property, the number is 36 inches. The 2010 ADA Standards, section 403.5.1, set the clear width of a walking surface at 36 inches minimum, narrowing to 32 inches for runs of up to 24 inches. A garden path that is not an accessible route to anything has no width standard at all.

If the walk comes out under 60 inches wide, PROWAG R302.3 adds one more requirement: a passing space of 60 by 60 inches at intervals of no more than 200 feet. The calculator counts those for you on long runs.

What municipalities actually build sits above the PROWAG minimum, because 48 inches leaves nothing for construction tolerance:

For a walk on your own property leading to a door, 3 feet is passable, 4 feet lets two people walk abreast, and 5 feet is generous. The calculator's width check tells you which of the two legal thresholds your number clears.

How thick, and where it changes

Four inches is the standard, and it is remarkably consistent across agencies. Iowa SUDAS puts it plainly: sidewalks "should be constructed of PCC with a minimum thickness of 4 inches," and at driveways the "minimum thickness is 6 inches, or the thickness of the driveway, whichever is greater." Montana DOT's drawing shows the same two numbers, 4 inches for the walk and 6 for the approach. So does FHWA's standard drawing E615-01, which puts 4 inches of concrete on 4 inches of bedding material.

The 6 inch driveway crossing is the one place a residential walk genuinely needs more concrete, and it is why this calculator has a field for it. A car crossing a 4 inch walk over a compacted base will usually survive; a delivery truck will not.

Thickness can also scale with width. One SUDAS-based municipal spec ties the two together: 4 and 5 foot walks at 4 inches minimum, 8 foot walks at 5 inches, and 10 feet or wider at 6 inches. That is a sensible rule for a wide walk, because a wider panel carries more restraint.

There is no national standard. ACI 332, the residential concrete code, covers footings, foundation walls and slabs on ground for dwellings, and exterior walkways are not in its scope. The closest thing to a national figure is an industry recommendation: Ohio Concrete's exterior flatwork recommendation sets a 3.5 inch minimum, and says exactly why: it is "the nominal depth of standard 2x4 lumber forms." The thinnest allowable walk in America is thin because of the lumber.

Control joints: the rule almost every calculator gets wrong

You will see this rule repeated everywhere: space control joints at 24 to 30 times the slab thickness. Two things are wrong with it as applied to a sidewalk.

First, the numbers are 24 to 36, not 24 to 30. NRMCA's bulletin on joints states that "the maximum joint spacing should be 24 to 36 times the thickness of the slab," with a hard cap of 15 feet and a shape rule that "the length should not exceed 1.5 times the width."

Second, and more important, it is the wrong rule for a walk. Apply it to a 4 inch sidewalk and you get 8 to 12 feet. Now look at what the agencies actually require. FHWA's standard drawing, note 2, says to "place contraction joints at intervals equal to the width of the sidewalk." Iowa SUDAS says the same thing. The MAG uniform specification used across Arizona uses 125 percent of the width. Cities that write a fixed number write 5 or 6 feet: Memphis specifies grooves "approximately 5 feet apart," West Palm Beach 5 feet, Ithaca no panel longer than 6 feet on any side.

So on a 4 foot walk, the joints go at 4 feet, not at 10. A calculator that applies only the thickness rule puts them roughly twice as far apart as any standard allows. The reason is the shape rule NRMCA states and the shorthand drops: on a 4 foot wide walk, a 10 foot panel is 2.5 times longer than it is wide, well past the 1.5 limit, and it will crack across the middle. This calculator spaces the joints on the width and reports the thickness rule only as a cross-check.

How deep

NRMCA sets the groove at "a minimum depth of 1/4 the thickness of the slab, but not less than 1 inch." Note where those two rules collide: on a 3.5 inch walk, a quarter of the thickness is 0.875 inch, which fails the 1 inch floor. The residential thickness range is exactly where the two diverge.

Agencies are not unanimous on the fraction either. Iowa SUDAS wants a third of the thickness for sawed joints. Ohio Concrete wants a third longitudinally and a quarter transversely. MAG sets a flat three quarters of an inch minimum. West Palm Beach asks for a 1.5 inch saw cut in a 4 inch walk, which is 37 percent. The calculator returns the NRMCA figure and the range around it.

On timing, NRMCA puts conventional saw cuts at 4 to 12 hours after finishing and early-entry dry cuts at 1 to 4 hours. Tooled joints go in while the concrete is still plastic.

Expansion joints go by location, not by interval

Control joints and expansion joints are different things, and the advice to "put an expansion joint every 10 feet" appears in no standard I could find. Here is what the real intervals look like:

A tenfold spread across five standards tells you the interval is not the point. What the standards agree on is where the joints go. MAG requires them "at all radius points, at both sides of each driveway, at both sides of each alley entrance." NRMCA requires isolation joints separating flatwork from "walls and footings" and separating "driveways and patios from sidewalks, garage slabs, stairs, lightpoles and other points of restraint."

That is the useful instruction. Put a full-depth joint wherever the walk meets something that will not move with it, then fill in the interval joints at whatever spacing your local standard names. The calculator defaults to 50 feet, which sits in the middle of the published band, and the field is editable.

Slope: do not aim for 2 percent

PROWAG R302.5.1 limits the cross slope of a pedestrian access route to 1:48, which the rule itself renders as 2.1 percent. The running slope limit, R302.4, is 1:20 or 5 percent, and where the adjacent street is steeper than that the walk may follow the street.

The mistake is treating 2 percent as a target. It is a ceiling, and a finished slab does not come out exactly where you screeded it. Agencies build the tolerance in themselves: Montana DOT specifies a 2 percent maximum with 1.5 percent shown as desirable, MnDOT requires that the cross slope "shall not exceed 0.02 ft./ft. as constructed," and Iowa SUDAS targets 1.5 percent with 2.0 as the maximum.

Build at 1.5 percent, which is about 3/16 inch of fall per foot of width, and you have room to be off. Build at exactly 2 percent and half the walk fails inspection.

The reason the margin is so tight is worth knowing: 1:48 is exactly a quarter inch per foot, which is also the minimum drainage slope ACI 302.1R asks for on an exterior slab. The accessibility ceiling and the drainage floor are the same number, so the compliant window is zero wide before tolerance is even considered. The concrete slope calculator has both halves of that, the conversion chart, and the 1971 highway study the 2 percent figure traces back to.

The base under it

Four inches of compacted granular base is the most common figure, but it is not a requirement, and the specs vary more than you would expect: MnDOT calls for 3 inches of Class 5, Montana DOT 2.5 inches of crushed aggregate course, FHWA 4 inches of bedding material, one Pennsylvania borough 4 inches of No. 2B stone, and one Illinois village 5 inches of CA6. WisDOT places base only "if the plans show" it, and Iowa SUDAS specifies no mandatory granular subbase under a sidewalk at all.

What the specs are firmer about is what to do with bad soil. MAG requires that "all soft or unsuitable material shall be removed to a depth of not less than 6 inches below subgrade elevation and replaced." Compaction is specified separately from thickness: West Palm Beach wants the subgrade compacted to 98 percent of maximum density under ASTM D1557.

Enter a base thickness in the optional panel and the calculator returns the cubic yards and the approximate tonnage, which is what a gravel yard will quote you. The gravel calculator handles a base on its own if you are ordering it separately.

What mix to order

There is no single national number. Across real specifications the range runs 3,000 to 4,500 psi:

• 3,000 psi: West Palm Beach, for sidewalks in the right of way
• 3,750 psi: PennDOT Class AA
• 4,000 psi at 28 days: Iowa SUDAS and one Illinois village ordinance, the most common figure
• 4,500 psi: Ohio Concrete's industry recommendation, higher than any agency spec here

Air entrainment matters more than the strength number anywhere that freezes. Iowa targets 7 percent with a 6 to 8.5 percent band, West Dundee 6 percent plus or minus 1, WisDOT 6 percent plus or minus 1.5, Ohio Concrete 6 percent plus or minus 2. A sidewalk is horizontal, exposed and salted, which is the worst combination there is for scaling. Specify air, and see concrete psi for how the strength classes relate.

Slump is the least standardized of the three. Most agencies set a cap rather than a range, typically 4 inches, and Iowa allows up to 4 inches for hand-finished work against 2.5 inches machine-finished. Ohio Concrete recommends 3 to 5 inches. If you are mixing from bags, the mix calculator and how to mix concrete cover the water side, where a gallon per cubic yard is about an inch of slump.

Does a sidewalk need wire mesh?

By the standards, usually not. WisDOT section 602 describes sidewalk work "with or without reinforcement" and says that "if required, use reinforcement conforming to, and place it as specified on, the plans." No reinforcement appears in Montana DOT's drawing, MnDOT's standard plan, FHWA's standard drawing, or Iowa SUDAS for a standard sidewalk.

At a driveway crossing, the near-universal answer is more thickness rather than steel: 6 inches, or the driveway thickness, whichever is greater. A minority of jurisdictions do require both, such as one Pennsylvania borough that calls for 4,000 psi at 6 inches "reinforced with 6x6 W2.9xW2.9 welded wire fabric" through driveway areas.

Worth being clear about why, because the common claim is that mesh stops cracking. It does not, and none of these documents credits it with that. Jointing is the crack control mechanism in every one of them. Reinforcement in a sidewalk standard appears for crack width control and load transfer, at driveways and where the walk crosses a utility trench, not as general insurance. Rebar and reinforcement goes through where steel does earn its place.

Forms and stakes

Form lumber is in the codes as nominal 2 inch stock rather than by name. Ithaca requires forms "of lumber two inches thick or of steel of equal strength, except on curves, where flexible strips may be used."

The practical issue nobody mentions: a 2x4 is 3.5 inches deep, not 4. A 4 inch walk formed with 2x4s is a 3.5 inch walk unless you set the forms half an inch proud of the subgrade, which is fiddly, or use 2x6 and strike the concrete at a line. The calculator names the lumber size for your thickness and flags the 4 inch case.

The calculator returns two times the length for the form lumber, which is both sides of the walk with no allowance for returns, stakes or waste. Buy longer boards than the run and cut.

Stake spacing has no standard behind it. I looked: nothing in the state DOT specifications, municipal codes, ASTM, or ACI's formwork guide addresses it. The 2 to 4 feet you see quoted everywhere is trade practice, and it is worth saying so rather than presenting it as a requirement. Closer on curves, closer in soft ground, and closer than you think if the concrete is wet.

What a sidewalk costs

The material side is firm. One cubic yard covers 81 square feet at 4 inches, and the ready-mix industry's own benchmarking survey puts the average selling price at $160 per cubic yard, which is about $2.00 per square foot of concrete. Add a granular base at roughly $0.30 to $0.50 per square foot and forms, and materials land near $3 per square foot.

Installed, published figures for a concrete sidewalk run about $6 to $12 per square foot, with labor the larger share. A narrow walk prices worse per foot than a wide one, because the crew, the forms and the short-load fee do not shrink with the pour.

The cost panel in the calculator prices the concrete, delivery and optional finishing labor from editable defaults. For the whole-job version, see the concrete cost calculator and concrete cost per square foot.

Sources

• US Access Board, PROWAG 2023 final rule, chapter R3, for the 48 inch route width, passing spaces and slope limits.
• 2010 ADA Standards, chapter 4, for the 36 inch walking surface width on private property.
• FHWA standard drawing E615-01, Concrete Sidewalk, for thickness, bedding and joints at the walk width.
• Iowa SUDAS Design Manual 12A-1, for width, thickness and the driveway crossing rule.
• NRMCA CIP 6, Joints in Concrete Slabs on Grade, for joint spacing, depth and sawing time.
• WisDOT standard specification 602, for expansion joints and optional reinforcement.
• Ohio Concrete, Industry Recommendation for Exterior Concrete Flatwork, for the 3.5 inch minimum and the mix recommendation.