Concrete Patio & Sidewalk Calculator: Yards and Bags for Walkways
This calculator sizes the concrete for patios, sidewalks, and walkways by taking your length, width, and thickness and returning cubic yards, bag counts, and cost. Most flatwork like this is poured 4 inches thick, so it defaults there while letting you adjust for thicker or L-shaped areas.
Estimated concrete
Estimates only. Add ~5–10% for waste. Bag yields: 40 lb ≈ 0.30, 60 lb ≈ 0.45, 80 lb ≈ 0.60 cu ft. Concrete ≈ 150 lb per cu ft.
How to Use the Patio & Sidewalk Calculator
- 1
Enter your dimensions
Type the length, width and thickness of your slab, footing or pad and choose your units, feet, inches or meters.
- 2
Get instant volume
See the result in cubic yards, cubic feet and cubic meters, plus weight, the moment you type, no page reloads.
- 3
Buy the right amount
We convert volume into the exact number of 40, 60 and 80 lb bags, truck loads and cost so you order without waste or shortfalls.
The formula
cubic yards = [Length_ft × Width_ft × (Thickness_in ÷ 12)] ÷ 27, then +10% waste
- ·Length_ft = walkway or patio length (ft)
- ·Width_ft = walkway or patio width (ft)
- ·Thickness_in = slab thickness (in), typically 4
- ·27 = cubic feet in one cubic yard
- ·+10% = spillage and grade allowance
Sidewalks and patios use the same flat-slab math as any slab. Keep width and length in feet and convert only the thickness from inches to feet by dividing by 12.
Worked examples
Example 1: 4 ft × 30 ft sidewalk, 4 in thick
- Area = 30 × 4 = 120 ft²
- Depth = 4 ÷ 12 = 0.333 ft
- Volume = 120 × 0.333 = 40 ft³
- Yards = 40 ÷ 27 = 1.48; +10% ≈ 1.63 yd³
Result: ≈1.63 cubic yards (order the 1.5-yd short load rounded up)
Example 2: 10 × 10 patio, 4 in thick, poured from bags
- Volume = 10 × 10 × (4 ÷ 12) = 33.33 ft³
- 80 lb bag yields 0.60 ft³
- Bags = 33.33 ÷ 0.60 = 55.6
- Round up = 56 bags
Result: 56 × 80 lb bags (about 1.23 yd³)
Concrete calculators by project type
Concrete bag yield & coverage
How much mixed concrete a standard bag yields, and how far a cubic yard goes at common slab depths.
| Bag size | Yield (cu ft) | Bags per cubic yard |
|---|---|---|
| 40 lb | 0.30 | 90 |
| 60 lb | 0.45 | 60 |
| 80 lb | 0.60 | 45 |
- 40 lb
- 60 lb
- 80 lb
Related guides
Patio & Sidewalk Concrete FAQs
How thick should a concrete sidewalk or patio be?
Sidewalks and patios are typically poured 4 inches thick over a compacted gravel base. Bump it to 5 or 6 inches only where vehicles might drive over the slab.
How much concrete do I need for a 10x10 patio?
A 10 ft by 10 ft patio at 4 inches thick needs about 1.23 cubic yards. That's roughly 21 eighty-pound bags if you're mixing by hand, though a small ready-mix load is usually easier.
How wide should a concrete walkway be?
A comfortable residential walkway is 36 to 48 inches wide, letting two people pass. Main entry paths often use 48 inches, while secondary garden paths can be as narrow as 30 inches.
How many bags of concrete for a sidewalk?
It depends on length, but figure about 45 eighty-pound bags per cubic yard. A 3 ft wide, 20 ft long sidewalk at 4 inches needs roughly 0.74 yards, or about 34 eighty-pound bags.
Do I need rebar or wire mesh in a patio?
For a 4-inch patio, welded wire mesh or fiber-reinforced concrete is common to limit cracking. Rebar is optional for standard patios but worth adding on larger slabs or poor soils.
How far apart should control joints be on a sidewalk?
Cut or tool control joints at a spacing in feet no greater than about 2 to 3 times the slab thickness in inches. For a 4-inch sidewalk, that means joints every 8 to 10 feet, and no wider than the walk itself.
How much more concrete does a 6-inch patio need than a 4-inch one?
Volume scales directly with thickness, so a 6-inch slab needs 50% more concrete than a 4-inch slab of the same footprint. A 10×10 patio jumps from about 33.3 ft³ (1.23 yd³) at 4 inches to 50 ft³ (1.85 yd³) at 6 inches. Only go to 6 inches if the surface will carry vehicles or heavy loads.
Should a sidewalk or patio slope for drainage?
Yes. Pitch the surface away from buildings at about 1/4 inch per foot, or roughly 2%, so water sheets off instead of pooling. Over a 4-foot-wide walk that is about 1 inch of fall across the width. The calculator volume is unaffected because the slope is tiny relative to slab thickness.
What base should go under a sidewalk or patio?
Lay 4 to 6 inches of compacted gravel or crushed stone over stripped, compacted subgrade before pouring. A firm base prevents settling and cracking and gives you a consistent slab thickness, which keeps your concrete estimate accurate. In freeze-prone regions a thicker gravel base helps with drainage and frost movement.
How long before I can walk on a new sidewalk?
Foot traffic is usually fine after 24 to 48 hours, once the surface is firm and no longer marks under pressure. Full design strength takes about 28 days of curing. Keep the slab damp or covered for the first several days to reduce surface cracking.
Can I pour a patio in separate sections?
Yes, and it is common for large patios or when you have limited help. Use form boards to create clean joints between pours, and treat each section's volume separately in the calculator. Planned joints between sections also double as control joints that manage cracking.
Do I need a permit to pour a sidewalk?
It depends on your municipality; public sidewalks in the right-of-way almost always require a permit and inspection, while a private backyard patio often does not. Check local rules before ordering concrete. Some areas also specify minimum thickness and slope for public walks.
How much concrete does a 4×30 ft sidewalk cost?
At 4 inches thick it needs about 40 ft³, or 1.48 cubic yards before waste. At a typical $145 per yard that is roughly $215 in ready-mix, plus any short-load and delivery fees. Bagged concrete would run about 67 of the 80 lb bags for the same volume.