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Construction

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Construction

Concrete Wall Calculator.

Estimates the volume of concrete needed for a wall, along with the number of 80 lb bags required.

Results update live as you type.
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Your inputs

How it works

  1. 1

    Convert thickness from inches to feet by dividing by 12.

  2. 2

    Multiply length by height to get the wall area in square feet.

  3. 3

    Multiply the area by the thickness in feet to get the volume in cubic feet.

  4. 4

    Divide the volume by 0.6 (cubic feet per 80 lb bag) and round up to get the number of bags.

length * height * (thickness / 12)

Frequently asked questions

How much does an 80 lb bag of concrete cover?

An 80 lb bag of concrete mix yields about 0.6 cubic feet when mixed with water.

Should I add extra concrete for waste?

It's recommended to add 5-10% extra to account for spillage, uneven surfaces, and variations in thickness.

Can I use this calculator for any wall shape?

This calculator assumes a rectangular wall. For walls with openings or irregular shapes, subtract those areas or break into sections.

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Results

Formula checked

Concrete Volume

106.667cu ft

80 lb Bags Needed178bags
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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 wall, along with the number of 80 lb bags required.

  1. Convert thickness from inches to feet by dividing by 12.
  2. Multiply length by height to get the wall area in square feet.
  3. Multiply the area by the thickness in feet to get the volume in cubic feet.
  4. Divide the volume by 0.6 (cubic feet per 80 lb bag) and round up to get the number of bags.

Formulas

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

Volume of a rectangular wall

V = L × H × T

Multiply the wall's length, height, and thickness (all in consistent units) to get the volume.

Example:

Input: L = 20 ft, H = 8 ft, T = 8 in (0.667 ft)

Calculation: 20 × 8 × 0.667

Result: ≈ 106.7 cu ft

Bags of concrete

Bags = ceil(V / 0.6)

Each 80 lb bag yields about 0.6 cubic feet, so divide the total volume by 0.6 and round up.

Example:

Input: V = 106.7 cu ft

Calculation: 106.7 / 0.6 ≈ 177.8

Result: 178 bags

Real-world use cases

Where this calculation shows up in everyday life.

Pouring a foundation wall

Estimate concrete for a basement or retaining wall before ordering.

Example: A 30 ft long, 9 ft high, 8 in thick wall needs about 180 cu ft.

Planning a garden wall

Calculate materials for a decorative or boundary wall.

Example: A 15 ft long, 3 ft high, 6 in thick wall uses about 22.5 cu ft.

Budgeting a construction project

Get a quick material count to compare quotes from suppliers.

Example: Compare bag vs. ready-mix costs for a large wall.

Tips and common mistakes

Tips

  • Always measure in the same units; convert inches to feet by dividing by 12.
  • Add 5-10% extra concrete for waste and uneven subgrades.
  • For large walls, consider ordering ready-mix concrete instead of bags for cost and labor savings.
  • Check the yield on your specific concrete mix bag, as it can vary slightly.

Common Mistakes to Avoid

  • Forgetting to convert thickness from inches to feet.
  • Not accounting for openings like doors or windows.
  • Rounding down the number of bags, which can leave you short.

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.