Slab Weight Calculator
Estimate how heavy a concrete slab is before you lift, prop, or transport it. Enter the slab length, width, and thickness in metres along with the concrete density in kg/m³ (preset to 2,400) and the page returns the self-weight in kilograms.
Your result will appear here.
Slab Weight Calculator online
Estimate the weight of a concrete slab from its length, width, thickness and density — for structural load checks, transport planning and precast lifting estimates.
How it works
The calculation is Weight = L × W × Thickness × Density. The first three inputs give the slab volume in m³; multiplying by density converts volume to mass. The density field defaults to 2,400 kg/m³, the standard value for normal-weight reinforced concrete, with the thickness field preset to 0.15 m.
Worked example
A slab 6 m × 4 m × 0.15 m at 2,400 kg/m³: volume = 6 × 4 × 0.15 = 3.6 m³; weight = 3.6 × 2,400 = 8,640 kg (8.64 tonnes, or about 19,050 lb). Per square metre that is 0.15 × 2,400 = 360 kg/m², a useful check figure when comparing against load tables.
Units
Output is in kilograms: 1,000 kg = 1 tonne (metric ton) ≈ 2,204.6 lb. Density pointers: plain concrete ≈ 2,300 kg/m³, normal reinforced concrete ≈ 2,400–2,500 kg/m³, lightweight concrete ≈ 1,600–1,900 kg/m³. If you know the mix is lightweight at 1,800 kg/m³, the same 3.6 m³ slab weighs 3.6 × 1,800 = 6,480 kg instead of 8,640 kg.
Practical tips
- Change the density for non-standard mixes. Using the 2,400 default for lightweight screed overstates the weight by up to a third.
- Include reinforcement only via density: the 2,400 default already allows for typical rebar content, so do not add bar weights on top for ordinary slabs.
- Check thickness with cores or drawings rather than the specification alone; a 170 mm as-built slab weighs 13% more than the 150 mm design (0.17 × 2,400 = 408 kg/m² vs 360 kg/m²).
- This is a self-weight estimate for planning lifts and supports, not a structural design. Crane picks, propping, and floor loadings must be verified by a qualified structural engineer against the project drawings.
Edge cases and limitations
- Hollow-core is not solid. Precast hollow-core planks carry voids that cut their weight to roughly two-thirds of a solid slab of the same depth — a 150 mm unit runs about 240 kg/m² against the solid slab's 360 kg/m². Use the manufacturer's kg/m² figure for planks, not this page's solid-section math.
- Toppings and screeds ride on top. A 50 mm sand-cement screed at about 2,100 kg/m³ adds roughly 105 kg/m² — nearly a third of a 150 mm slab's own weight. Floor build-ups belong in the load total even though this page counts the slab alone.
- Openings deduct honestly. Stairwells, lift shafts and service cores remove their full plan area from the slab: deduct opening area × thickness × density. On heavily-serviced floors the deduction regularly exceeds 10%.
- Thickness is the sensitive input. Weight scales linearly with thickness, and as-built slabs run thicker than drawn where the subgrade dips — the delivery-ticket mismatch in the FAQ usually starts there, not with the density.
Privacy and browser processing
The calculation runs entirely in your browser — the dimensions you enter are never uploaded.
Frequently asked questions
What density should I enter for normal reinforced concrete?
Keep the preset 2,400 kg/m³, which is the widely used design value for normal-weight reinforced slabs. For heavily reinforced sections some designers use 2,500 kg/m³ — on the 3.6 m³ example that gives 3.6 × 2,500 = 9,000 kg instead of 8,640 kg.
How heavy is 1 m² of 150 mm slab?
Multiply thickness by density: 0.15 × 2,400 = 360 kg/m². A 100 mm slab is 0.10 × 2,400 = 240 kg/m², and a 200 mm slab is 0.20 × 2,400 = 480 kg/m², so weight scales linearly with thickness.
Can I weigh a precast panel before lifting it?
Yes — enter its exact dimensions. A panel 3 m × 1.5 m × 0.2 m at 2,400 kg/m³ gives 3 × 1.5 × 0.2 = 0.9 m³, then 0.9 × 2,400 = 2,160 kg. Add rigging weight on top, and confirm the crane chart with a lift plan rather than relying on this figure alone.
Why is my slab heavier than the concrete delivery ticket suggests?
Delivery volume is the neat pour (3.6 m³ here), but as-built thickness often runs over — 6 × 4 × 0.17 m is 4.08 m³, giving 4.08 × 2,400 = 9,792 kg. Re-measure the cast thickness and re-run the tool with the actual figure.