Concrete is heavy — deceptively so. A modest 10 × 10 ft slab at 4 inches weighs about 5,000 lb, and a single cubic yard tips the scales at roughly two tons. Knowing the weight matters for delivery access, trailer limits, crane picks, dead-load calculations and even whether your floor can carry the slab you’re planning. The formula is simple; the density number is where the detail lives.
The concrete weight formula
Weight = Volume × Density
That’s it. The only decision is which density to use, because it depends on the mix. Here are the standard values:
| Concrete type | Density (kg/m³) | Density (lb/ft³) |
|---|---|---|
| Normal-weight | 2,400 | 150 |
| Reinforced | 2,500 | 156 |
| Lightweight | 1,800 | 112 |
| High-strength / high-density | 2,600+ | 162+ |
Normal-weight concrete at 2,400 kg/m³ (150 lb/ft³) is the default for almost every residential and commercial pour. Use it unless you have a specific lightweight or heavyweight mix.
Weight per common unit
Because most people order by the yard or the meter, it’s worth memorizing the per-unit weights of normal concrete:
| Unit of volume | Approx. weight |
|---|---|
| 1 cubic foot | 150 lb (68 kg) |
| 1 cubic yard | 4,050 lb (1,839 kg) |
| 1 cubic meter | 2,400 kg (5,290 lb) |
| 4-inch slab, per ft² | 50 lb (23 kg) |
That last row is a handy shortcut: a 4-inch slab weighs about 50 lb per square foot. So a 200 ft² patio slab weighs roughly 10,000 lb — five tons sitting on your sub-base.
Worked example
Take a 12 ft × 12 ft driveway section at 6 inches thick:
- Volume = 12 × 12 × 0.5 = 72 ft³
- Weight = 72 ft³ × 150 lb/ft³ = 10,800 lb (about 5.4 tons)
If that same slab were reinforced, use 156 lb/ft³ instead: 72 × 156 = 11,232 lb. The steel adds a few hundred pounds. You can size the reinforcement itself with the rebar calculator, and check the volume first with the volume calculator.
Why density varies
- Reinforced concrete is heavier because embedded steel (rebar and mesh) adds roughly 100 kg/m³. Steel weighs about 7,850 kg/m³, so even a modest reinforcement ratio nudges the total up.
- Lightweight concrete uses expanded clay, shale or slate aggregate to drop density to 1,800 kg/m³ or lower — useful for upper floors and precast panels where dead load is the enemy.
- High-density concrete uses heavy aggregates like magnetite or barite to exceed 2,600 kg/m³, mainly for radiation shielding and counterweights.
- Fresh vs cured: fresh concrete weighs slightly more than fully cured concrete, since some mix water is later lost to hydration and evaporation.
Where weight actually matters
- Delivery and access: a loaded ready-mix truck can weigh 30 tons or more. Soft ground, culverts and long driveways all factor into whether the truck can reach the pour.
- Structural dead load: every suspended slab and beam must carry its own weight before any live load. This is why the 8-inch slab calculator and load-related tools matter for heavy pours.
- Hauling debris: breaking out an old slab? A 200 ft² × 4-inch slab is five tons of rubble — well past most trailer ratings in a single load.
- Estimating from the mix: if you know the grade and mix, the material calculator and weight calculator turn volume into cement, aggregate and total mass.
Quick reference
To get concrete weight fast: find the volume, then multiply by 150 lb/ft³ (imperial) or 2,400 kg/m³ (metric) for normal concrete. Bump to 156 lb/ft³ or 2,500 kg/m³ if it’s reinforced. For anything beyond a back-of-envelope figure — including lightweight and high-density mixes — the concrete weight calculator gives kilograms, tonnes, pounds and US tons in one step.