Physics

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Physics

Concrete Slab Weight Calculator.

Estimates the total weight of a concrete slab based on its dimensions and the density of the concrete mix.

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

    Calculate the slab volume: length × width × thickness (in feet).

  3. 3

    Multiply the volume by the selected concrete density (lb/ft³).

  4. 4

    The result is the total weight in pounds.

length * width * (thickness / 12) * (density == 'lightweight' ? 90 : density == 'heavy' ? 175 : 145)

Frequently asked questions

What is the typical density of normal concrete?

Normal concrete weighs about 145 lb/ft³. Lightweight mixes are around 90 lb/ft³, and heavy mixes can be 175 lb/ft³ or more.

How do I convert the weight to tons?

Divide the weight in pounds by 2,000 to get short tons (US). For example, 4,000 lb is 2 tons.

Does the calculator account for reinforcement steel?

No, it estimates the weight of the concrete only. Rebar and other reinforcements add extra weight, typically a few percent.

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Total Weight

0lb

Volume0ft³
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Estimate for general guidance only — verify important decisions with an appropriate professional.

How it works

Estimates the total weight of a concrete slab based on its dimensions and the density of the concrete mix.

  1. Convert thickness from inches to feet by dividing by 12.
  2. Calculate the slab volume: length × width × thickness (in feet).
  3. Multiply the volume by the selected concrete density (lb/ft³).
  4. The result is the total weight in pounds.

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 the volume in cubic feet.

Example:

Input: L = 10 ft, W = 8 ft, T = 4 in (0.333 ft)

Calculation: 10 × 8 × 0.333 = 26.64 ft³

Result: ≈ 26.64 ft³

Weight from density

W = V × ρ

Multiply the volume by the density of concrete (lb/ft³) to get the total weight.

Example:

Input: V = 26.64 ft³, ρ = 145 lb/ft³

Calculation: 26.64 × 145 = 3,862.8 lb

Result: ≈ 3,863 lb

Real-world use cases

Where this calculation shows up in everyday life.

Planning a concrete pour

Estimate the weight of a slab to ensure your forms and subgrade can support it.

Example: A 10×8 ft slab, 4 in thick, weighs about 3,867 lb.

Transportation and lifting

Know the weight of precast panels or slabs for crane and truck capacity planning.

Example: A 5×5 ft, 6 in thick lightweight slab weighs about 1,125 lb.

Structural load calculations

Use the slab weight as a dead load when designing foundations or supports.

Example: A 20×12 ft, 6 in thick heavy slab weighs about 21,000 lb.

Tips and common mistakes

Tips

  • Always measure dimensions in the same units; convert inches to feet by dividing by 12.
  • If you know the exact mix density, use it instead of the typical values.
  • Add 5-10% extra weight for rebar, mesh, or moisture if needed.
  • For large slabs, consider the weight per square foot: thickness (in) × density / 12.

Common Mistakes to Avoid

  • Forgetting to convert thickness from inches to feet, leading to a weight 12 times too high.
  • Using the density of water (62.4 lb/ft³) instead of concrete (145 lb/ft³).
  • Ignoring the difference between lightweight and normal concrete when selecting the mix.

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.