Concrete Volume Calculator
Calculate cubic yards, cubic meters, and premix bags of concrete required for construction slabs and footings.
About Concrete Volume Calculations
Ordering ready-mix concrete requires calculating volume by multiplying length, width, and depth, while converting all three dimensions into uniform measurement units.
Formulas
- Thickness in Feet: Depth (inches) / 12
- Cubic Feet: Length (ft) × Width (ft) × Thickness (ft)
- Cubic Yards: Cubic Feet / 27
- Cubic Meters: Cubic Yards × 0.764555
Worked Example
For a 12 ft × 10 ft patio slab poured at a standard 4-inch thickness with a 10% contingency buffer:
- Raw volume: 12 × 10 × (4/12) = 40 cubic feet = 1.48 cubic yards
- With 10% waste buffer: 1.63 cubic yards (~1.25 m³)
- Requires approximately 73 pre-mixed 80-lb bags
Frequently Asked Questions
Why is a waste margin necessary?
A 5% to 10% waste contingency accounts for subgrade settling, uneven soil excavations, formwork deflection, and spillage.
How many 60 lb or 80 lb bags make up one cubic yard?
One cubic yard requires approximately forty-five 80-lb bags or sixty 60-lb pre-mixed bags.
What is the standard residential slab thickness?
Sidewalks and residential patios typically require 4 inches; standard car driveways require 4 to 5 inches; heavy RV pads require 6 inches.
How long must concrete cure before bearing load?
Concrete achieves approximately 70% of its compressive strength within 7 days, reaching full structural design strength at 28 days.
Calculate in three steps
- 1Enter your valuesUse the fields above and check the units shown beside each input.
- 2Run the calculationSelect Calculate to refresh the result with your latest values.
- 3Review or shareCompare the result, reset the form, print it, or share this page.