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Concrete Volume Calculator

Estimate concrete quantity for slabs, footings, columns, and beams. Enter dimensions in feet, inches, meters, or centimeters and get results in cubic feet, cubic yards, and cubic meters — with a separate waste allowance.

1 Select shape

2 Measurement units

3 Dimensions

4 Waste allowance

10%

Estimated Concrete Required

0.00

cubic yards (with waste)

Cubic feet

0.00

Cubic meters

0.00

Calculation breakdown

Base volume
0.00 ft³
Waste allowance
0.00 ft³ (10%)
Total required
0.00 ft³

Selected dimensions

All units

ft³
0.00
yd³
0.00
m³
0.00

⚠️ This is a volume estimate only. Concrete weight varies by mix (typically 140–150 lb/ft³). Order 5–10% extra for uneven subgrade and spillage.

How to Calculate Concrete Volume

Whether you're pouring a driveway slab, setting fence posts, or forming a foundation, ordering the right amount of concrete is critical. Too little and you'll scramble for a second delivery; too much and you're paying for waste. This guide explains the formulas behind our concrete volume calculator, how to convert between cubic feet, cubic yards, and cubic meters, and how to account for waste.

The Basic Formula

For any rectangular prism — which covers slabs, footings, rectangular columns, and beams — volume is simply:

Volume = Length × Width × Height (or Depth)

For a circular column, use the cylinder formula:

Volume = π × r² × Height

Where r is the radius (half the diameter) and π ≈ 3.14159.

Cubic Feet vs Cubic Yards

In the United States, concrete is ordered in cubic yards (yd³). One cubic yard is a cube 3 ft × 3 ft × 3 ft, which equals 27 cubic feet. So:

Cubic Yards = Cubic Feet ÷ 27

In metric countries, concrete is ordered in cubic meters (m³). One cubic meter = 35.3147 cubic feet. Our calculator handles all conversions automatically when you select your input units.

Concrete Waste Allowance

No concrete pour is perfectly efficient. Concrete can be lost to:

  • Uneven subgrade that absorbs extra material
  • Spillage during chute or pump placement
  • Formwork deflection or leaks
  • Over-excavation around footings
  • Minor measurement rounding

A standard waste allowance is 5–10%. For complex shapes, deep footings, or first-time pours, 10–15% is safer. Our calculator keeps waste separate from the base volume so you can see exactly how much extra you're ordering.

Worked Examples

Example 1: Slab

A patio slab is 12 ft long, 10 ft wide, and 4 inches thick. Convert thickness to feet: 4 ÷ 12 = 0.333 ft.

Volume = 12 × 10 × 0.333 = 40 ft³
Cubic yards = 40 ÷ 27 = 1.48 yd³
With 10% waste = 1.63 yd³

Example 2: Circular Column

A sonotube column is 12 inches in diameter and 8 ft tall. Radius = 6 in = 0.5 ft.

Volume = π × 0.5² × 8 = 3.14159 × 0.25 × 8 = 6.28 ft³
Cubic yards = 6.28 ÷ 27 = 0.23 yd³

Example 3: Footing

A continuous footing is 24 ft long, 16 inches wide, and 8 inches deep. Convert: 16 in = 1.333 ft; 8 in = 0.667 ft.

Volume = 24 × 1.333 × 0.667 = 21.33 ft³
Cubic yards = 21.33 ÷ 27 = 0.79 yd³

Practical Ordering Considerations

  • Ready-mix vs bags: Ready-mix trucks typically have a minimum order (often 1 yd³). Small projects may be better with bagged concrete — one 80 lb bag yields about 0.6 ft³.
  • Weight vs volume: This calculator gives volume. Concrete weight depends on the mix — normal-weight concrete is about 145 lb/ft³ (3,915 lb/yd³).
  • Subgrade prep: Compacted gravel base reduces concrete loss into soil. If your subgrade is loose, add 5% more waste.
  • Weather: Hot, windy conditions can cause rapid evaporation. Have extra help and a curing plan ready.
  • Round up: Always round your final order up to the nearest quarter-yard. Running short mid-pour is far worse than having a small leftover.

Frequently Asked Questions

How do I calculate concrete volume for a slab? ▾

Multiply length × width × thickness (all in the same unit). For a 12 ft × 10 ft slab that's 4 inches thick: convert 4 in to 0.333 ft, then 12 × 10 × 0.333 = 40 cubic feet. Divide by 27 for cubic yards (1.48 yd³). Add 10% waste for a safe order.

How many cubic feet are in a cubic yard of concrete? ▾

There are 27 cubic feet in one cubic yard (3 ft × 3 ft × 3 ft = 27 ft³). To convert cubic feet to cubic yards, divide by 27.

What waste percentage should I use for concrete? ▾

5% for simple, well-prepped slabs. 10% is the standard allowance for most projects. Use 15% for footings, deep forms, or complex shapes where subgrade irregularities and spillage are more likely.

How do I calculate concrete for a circular column? ▾

Use the cylinder formula: π × radius² × height. If your column is 12 inches in diameter, the radius is 6 inches (0.5 ft). For an 8 ft column: 3.14159 × 0.5² × 8 = 6.28 ft³. Divide by 27 for cubic yards.

Does this calculator account for concrete weight? ▾

No — this is a volume calculator. Concrete weight varies by mix design. Normal-weight concrete is roughly 145 lb/ft³ (about 3,915 lb/yd³). Lightweight mixes can be significantly lighter. Contact your ready-mix supplier for exact weight per yard.

Can I use this for footing and beam calculations? ▾

Yes. Footings and beams are rectangular prisms, so the same length × width × height formula applies. Select "Footing" or "Beam" from the shape menu and enter your dimensions.

How many bags of concrete do I need? ▾

One 80 lb bag of concrete mix yields approximately 0.6 cubic feet. One 60 lb bag yields about 0.45 ft³. Divide your total cubic feet by the yield per bag, then round up. For projects over 1 cubic yard, ready-mix is usually more economical.

What's the difference between cubic yards and cubic meters? ▾

Cubic yards (yd³) are used in the US and UK for ordering ready-mix. Cubic meters (m³) are standard in most other countries. One cubic meter = 1.30795 cubic yards = 35.3147 cubic feet. Our calculator outputs all three units simultaneously.