Construction

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Construction

Concrete Sidewalk Calculator.

Estimates the volume of concrete needed for a sidewalk and the number of 60-lb bags required.

Results update live as you type.
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Your inputs

How it works

  1. 1

    Measure the length and width of the sidewalk in feet.

  2. 2

    Measure the thickness in inches and convert to feet by dividing by 12.

  3. 3

    Multiply length × width × thickness (in feet) to get cubic feet.

  4. 4

    Divide the cubic feet by 0.45 to estimate the number of 60-lb bags, rounding up.

length * width * (thickness / 12)

Frequently asked questions

How much area does one 60-lb bag of concrete cover?

A 60-lb bag yields about 0.45 cubic feet, so at 4 inches thick it covers roughly 1.35 square feet.

Should I order extra concrete?

It's wise to add 5-10% for waste, spillage, or uneven subgrade. Adjust the length and width slightly or add a buffer when buying bags.

Can I use this calculator for a patio or driveway?

Yes, the same volume formula applies. Just adjust the thickness and dimensions accordingly.

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Results

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Concrete Volume

0cu ft

60-lb Bags Needed0bags
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Estimate for general guidance only — verify important decisions with an appropriate professional.

How it works

Estimates the volume of concrete needed for a sidewalk and the number of 60-lb bags required.

  1. Measure the length and width of the sidewalk in feet.
  2. Measure the thickness in inches and convert to feet by dividing by 12.
  3. Multiply length × width × thickness (in feet) to get cubic feet.
  4. Divide the cubic feet by 0.45 to estimate the number of 60-lb bags, rounding up.

Formulas

The math behind this calculator, written out so you can verify the result.

Volume of a rectangular slab

V = L × W × T

Multiply length, width, and thickness (all in feet) to get cubic feet of concrete.

Example:

Input: L = 20 ft, W = 3 ft, T = 4 in (0.333 ft)

Calculation: 20 × 3 × 0.333 = 20 cu ft

Result: ≈ 20 cu ft

Bags from volume

Bags = V / 0.45

Each 60-lb bag yields about 0.45 cubic feet. Divide total volume by 0.45 and round up.

Example:

Input: V = 20 cu ft

Calculation: 20 / 0.45 = 44.44

Result: ≈ 45 bags

Real-world use cases

Where this calculation shows up in everyday life.

Home sidewalk replacement

Estimate concrete needed for a standard 3-ft wide walkway.

Example: 20 ft long, 3 ft wide, 4 in thick → 20 cu ft

Garden path

Plan a narrow path with thinner concrete to save material.

Example: 30 ft long, 2 ft wide, 3 in thick → 15 cu ft

Contractor bidding

Quickly calculate material costs for multiple sidewalk sections.

Example: Sum volumes of each section

Tips and common mistakes

Tips

  • Always measure in feet; convert inches to feet by dividing by 12.
  • Add 5-10% extra for waste and uneven ground.
  • For a stronger sidewalk, consider 5-6 inches thickness if vehicles will cross it.
  • Check local building codes for minimum thickness requirements.

Common Mistakes to Avoid

  • Forgetting to convert thickness from inches to feet.
  • Using the bag yield for 80-lb bags (0.6 cu ft) instead of 60-lb (0.45 cu ft).
  • Not rounding up the number of bags, leading to a shortage.

Assumptions and limitations

  • Use the stated inputs and units.
  • Results are estimates for planning and education.
  • Check measurements and source data before making an important decision.