How it works
The calculator finds the volume from the shape you choose and multiplies it by the density.
Slab: Volume = Length × Width × Thickness × Pieces
Cylinder: Volume = π × (Diameter ÷ 2)² × Height × Pieces
Weight = Volume × Density
The presets are typical figures from the FHWA Lightweight Concrete Bridge Design Primer: 145 lb/cu ft for normal-weight concrete, 5 lb/cu ft more for reinforced concrete, and 115 lb/cu ft within the 110–125 lb/cu ft range it gives for lightweight concrete in bridges. A 10 × 10 ft slab 4 in thick holds 33.3 cu ft and weighs about 4,833 lb, or 2.4 short tons.
Units are converted internally, so you can mix feet, inches and meters. The result is an estimate for planning transport and handling, not a structural or lifting calculation.
Worked example
Inputs
- Shape
- Slab, pad or block (length × width × thickness)
- Length
- 10 ft
- Width
- 10 ft
- Thickness
- 4 in
- Number of pieces
- 1
- Type of concrete
- Normal-weight, plain – 145 lb/cu ft (2,323 kg/m³)
Result
- Weight of concrete
- 2.42 short tons (4,833 lb)
- Volume
- 1.23 cu yd (33.33 cu ft)
- Density used
- 145 lb/cu ft
Common mistakes
- Confusing pounds and short tons with kilograms and tonnes. One US short ton is 2,000 lb (907 kg); a metric tonne is 1,000 kg.
- Using the plain-concrete figure for a heavily reinforced element. Steel bars add weight; FHWA notes that reinforced concrete is usually taken as about 5 lb/cu ft heavier.
- Measuring the planned thickness instead of the actual one. An extra half inch over a whole slab adds a lot of weight.
- Rating a hoist, trailer or floor from this estimate. Lifting and structural loads need the real weight and a qualified person.
Assumptions and limits
- Volume is length × width × thickness, π × (diameter ÷ 2)² × height, or the volume you enter, times the number of pieces.
- Weight = volume × density. Presets are typical values from FHWA-HIF-19-067; the concrete you have may be lighter or heavier.
- The weight is that of hardened concrete in place; wet concrete, forms and reinforcement accessories are not counted separately.
Frequently asked questions
How much does a cubic yard of concrete weigh?
At the typical normal-weight density of 145 lb/cu ft, 27 cu ft weighs 3,915 lb, just under 2 short tons. At 150 lb/cu ft for reinforced concrete it is 4,050 lb.
How much does a cubic meter of concrete weigh?
About 2,320 kg at 145 lb/cu ft, or about 2,400 kg at 150 lb/cu ft. FHWA gives a typical range of 140–155 lb/cu ft (about 2,240–2,480 kg/m³) for normal-weight concrete.
How heavy is a 4 inch concrete slab per square foot?
A 4 in slab is 1/3 cu ft per square foot, so at 145 lb/cu ft it weighs about 48 lb per square foot.
What is lightweight concrete?
Concrete made with lightweight aggregate. The FHWA primer gives typical densities of 110–125 lb/cu ft for bridges and as low as 90 lb/cu ft for all-lightweight concrete. Use your supplier’s figure if you have it.
Sources
- Lightweight Concrete Bridge Design Primer (FHWA-HIF-19-067), November 2021 — Federal Highway Administration, U.S. Department of Transportation. "typical normal-weight concrete density of 0.145 kcf" (145 lb/cu ft; range 0.140–0.155 kcf); reinforced concrete "taken as 0.005 kcf greater than the density for plain concrete" (preset 150 lb/cu ft); lightweight concrete for bridges "typically varies from 0.110 to 0.125 kcf", as low as 0.090 (preset 115 lb/cu ft).
- NIST Handbook 44, Appendix C – General Tables of Units of Measurement — National Institute of Standards and Technology. Exact unit definitions: 1 in = 2.54 cm, 1 yd³ = 27 ft³, 1 US gal = 231 in³, 1 lb = 0.45359237 kg.
Method reviewed November 6, 2026