Show the math
- Convert to feet (inches ÷ 12, centimeters ÷ 30.48): Length 30 ft; Width 4 ft; Thickness 4 in = 0.3333 ft
- Volume = 30 × 4 × 0.3333 × 1 = 40 ft³
- Net volume = 40 ft³ ÷ 27 = 1.4815 yd³ (× 0.0283168 = 1.1327 m³)
- Order quantity = 1.4815 yd³ × (1 + 10%) = 1.6296 yd³ = 44 ft³
- 80 lb bags = 44 ft³ ÷ 0.6 ft³ per bag = 73.33 → 74 bags (always round up)
- Weight = 44 ft³ × 150 lb/ft³ = 6,600 lb
How to measure
Measure the walkway along its centerline for the length and across it for the width. A path that is 4 ft wide for most of its length but widens to 5 ft at a door should be calculated in two pieces. Add the landing at the door as a separate rectangle.
Thickness is commonly 4 in for walkways, with 5 or 6 in where a driveway crosses the sidewalk. Public sidewalks have their own standards, so check with the municipality for widths, thickness and slope.
Worked example: a 30 ft walk, 4 ft wide
- Convert to feet (inches ÷ 12, centimeters ÷ 30.48): Length 30 ft; Width 4 ft; Thickness 4 in = 0.3333 ft
- Volume = 30 × 4 × 0.3333 × 1 = 40 ft³
- Net volume = 40 ft³ ÷ 27 = 1.4815 yd³ (× 0.0283168 = 1.1327 m³)
- Order quantity = 1.4815 yd³ × (1 + 10%) = 1.6296 yd³ = 44 ft³
- 80 lb bags = 44 ft³ ÷ 0.6 ft³ per bag = 73.33 → 74 bags (always round up)
- Weight = 44 ft³ × 150 lb/ft³ = 6,600 lb
| Quantity | Result |
|---|---|
| Net volume | 1.481 yd³ (40.00 ft³, 1.133 m³) |
| Order with 10% waste | 1.63 yd³ (1.25 m³) |
| 80 lb bags | 74 |
| 60 lb bags | 98 |
| Weight at 150 lb/ft³ | 6,600 lb |
Order 1.63 yd³, or 74 80 lb bags. A 30 ft walk is a one-day job with bags and a wheelbarrow. A 100 ft public sidewalk at the same width needs 5.43 yd³, which calls for a truck.
Concrete per linear foot
It helps to remember how much a foot of walkway holds. Multiply the figure by the length to cross-check any estimate.
| Width | 4 in thick | 5 in thick | 6 in thick |
|---|---|---|---|
| 3 ft | 1.00 ft³ | 1.25 ft³ | 1.50 ft³ |
| 4 ft | 1.33 ft³ | 1.67 ft³ | 2.00 ft³ |
| 5 ft | 1.67 ft³ | 2.08 ft³ | 2.50 ft³ |
| 6 ft | 2.00 ft³ | 2.50 ft³ | 3.00 ft³ |
Control joints and expansion joints
Sidewalk panels crack where they are weakest, so you decide where. The usual practice is to groove the surface at spacing roughly equal to the width for a path, up to 24 to 36 times the thickness for a slab (ACI 302.1R). For a 4 ft walk that is every 4 to 5 ft by the common practice and no more than 8 to 12 ft by the ACI figure. Use an isolation (expansion) joint where the walk meets a driveway, a step or a building.
Control joints should be cut or tooled to a depth of about one quarter of the thickness, which is 1 in on a 4 in slab. Read the control joints guide before the pour.
Accessibility and public standards
If the sidewalk is part of an accessible route, width, cross slope and running slope are regulated. In the United States, accessible routes generally require a clear width of at least 36 in, and passing spaces or turning areas are required at intervals. Public right-of-way sidewalks are governed by the local authority. This calculator gives quantities only: confirm design requirements with the city or an engineer.
Mistakes to avoid
- Forgetting to include the width variation at doorways and curb ramps.
- Pouring against a slope without checking drainage.
- Skipping joints and ending up with random cracks.
- Not including a gravel base.
- Calculating walkway length from the plan, which may include areas covered by buildings.
Frequently asked questions
How many yards of concrete for a sidewalk?
Length × width × thickness in feet divided by 27. A 100 ft sidewalk, 4 ft wide and 4 in thick is 133.3 ft³, or 4.94 yd³, before waste.
How thick should a concrete sidewalk be?
Four inches is typical for residential walkways. Thicker sections are used where vehicles cross.
How wide is a standard sidewalk?
Residential walkways are often 3 to 4 ft wide, public sidewalks are often 5 ft or wider. Local standards govern.
How many bags for a 4 × 20 ft path?
49 bags of 80 lb mix at 4 in thick with 10% waste.
How far apart should sidewalk joints be?
A common practice is about the width of the walk, no more than 24 to 36 times the thickness in ACI guidance.
Do I need a permit?
Public sidewalks nearly always require a permit. Private paths may not. Ask your local building department.
Sources
Estimate only. Results depend on the numbers you enter, ground conditions and your supplier. For structural work consult a licensed engineer and follow local codes. Brand names such as Quikrete and Sakrete are used only to cite published product data. This site is not affiliated with any brand.