Volume formula
length (ft) × width (ft) × thickness (in) ÷ 12 ÷ 27 = yd³
Example: 20 × 4 × 4 ÷ 12 ÷ 27 = 0.99 yd³ net.
Concrete planning estimate
Concrete Sidewalk Calculator
Estimate concrete volume, bag count, gravel base, and rough material cost for a sidewalk or walkway. The sidewalk preset uses 4 in thickness, 4 in road base, wire mesh reinforcement, and a 5% waste factor.
What this sidewalk calculator estimates
The walkway preset applies standard residential sidewalk defaults: 4 in slab thickness, 4 in road base, wire mesh reinforcement, and 3000 psi (M250) concrete.
- Concrete volume in cubic yards or cubic meters.
- 40 lb, 60 lb, and 80 lb bag counts rounded up to whole bags.
- Compacted road-base volume and approximate weight.
- Wire mesh planning area for light reinforcement.
- Form board count from sidewalk perimeter.
- Rough material cost range.
Sidewalk concrete formula
Sidewalks are a simple slab calculation — length and width define the area, thickness determines depth.
Joint spacing
Control joints are typically cut every 4–8 ft on a sidewalk (matching 24–30× slab thickness). A 4 in sidewalk needs joints roughly every 8 ft.
Driveway crossings
Where a sidewalk crosses a driveway apron, increase thickness to 6 in and use rebar reinforcement to handle vehicle loads.
Common sidewalk size estimates
Pre-calculated for 4 in thickness, M250 concrete, 5% waste, and 4 in road base.
| Sidewalk size | Net yd³ | Ordered yd³ | 80 lb bags |
|---|---|---|---|
| 3 ft × 20 ft × 4 in | 0.74 | 0.78 | 36 |
| 4 ft × 20 ft × 4 in | 0.99 | 1.04 | 47 |
| 4 ft × 40 ft × 4 in | 1.98 | 2.08 | 95 |
| 5 ft × 50 ft × 4 in | 3.09 | 3.24 | 148 |
| 5 ft × 100 ft × 4 in | 6.17 | 6.48 | 295 |
Concrete sidewalk calculator FAQ
How thick should a concrete sidewalk be?
Residential sidewalks are typically 4 in thick. Sidewalks that cross driveways or carry heavier traffic may be 5–6 in. Many municipalities specify minimums in their standards.
How wide should a concrete sidewalk be?
Residential walkways are typically 3–4 ft wide. Public sidewalks often require 5 ft or more to meet ADA/accessibility standards. Check local code or HOA requirements.
How much concrete for a 4 ft wide sidewalk?
A 4 ft wide × 20 ft long × 4 in thick sidewalk needs about 0.99 yd³ net. With 5% waste, order about 1.04 yd³ — roughly 47 bags of 80 lb concrete.
How far apart should control joints be in a sidewalk?
Control joints are typically spaced every 4–8 ft for a 4 in sidewalk (the 24× thickness rule gives 8 ft as a maximum). Shorter joints are common near corners or driveway crossings.
Do I need a permit for a residential sidewalk?
Requirements vary. Front-yard public sidewalks often have municipal requirements, while backyard walks may not need a permit. Check with your local building department first.
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Next planning steps
Planning estimates only
These are rough material estimates for planning purposes. They are not purchasing guarantees, engineering designs, or code compliance guidance. Check local code for required width, thickness, reinforcement, and permit requirements before starting work.