Example 1
- 5 × 4 × 0.1 m
- +5% waste
- 0 deductions
2.1 m³
A basic slab case where volume is the starting point for ordering and cost planning.
Concrete calculator
Enter length, width, and thickness in meters. The calculator multiplies the three sizes, adds waste, and subtracts deductions. A 5 by 4 m slab 10 cm thick at 5% is 2.1 m³. A 10 by 0.4 by 0.5 m footing at 10% is 2.2 m³. Six 0.3×0.3×1 m posts at 5% are 0.567 m³.
Also useful: mortar requirement, cement in mortar. Article: how much concrete to order.
Results
Length, Width, Height / thickness and Number of elements. The result shows up here.
How the results are calculated
The concrete calculator counts volume to order. The formula is length times width times height times the number of elements times (1 plus waste), then minus deducted volume. The result does not go below zero. A 10 cm slab thickness is 0.1 m, not 10.
A 5 by 4 m patio 10 cm thick at 5% waste is 2.0 m³ plus 0.1, so 2.1 m³. A 10 by 0.4 by 0.5 m footing at 10% is 2.2 m³. Six 30 by 30 cm posts a meter high at 5% give 0.567 m³. Twelve 1.2 by 0.3 by 0.18 m treads at 8% are about 0.84 m³.
Type length, width, and height or thickness in the same unit, usually meters. Element count, deductions, waste, and price are optional. An empty count means one pour. A comma and a period are the same size, so 0.1 and 0,1 are 10 cm.
A mortar bed lives on mortar requirement, cement in a mix on cement in mortar. Paint does not use cubic meters. Sand and gravel under a slab are separate bulk-volume cards.
Five percent waste on a 2 m³ slab is an extra 0.1 m³, because the pump and an uneven base eat the rest. Dry-mix bags round up on the mortar-bags page; here you stay in m³. Typing 10 as thickness instead of 0.1 overstates the pour a hundred times.
Type 5, 4, and 0.1, set 5%, and match 2.1 m³. Then 10, 0.4, and 0.5 at 10%: 2.2 m³ for the footing.
How to use this calculator
- Type length, width, and thickness in the header unit. A 10 cm slab is 0.1, not 10.
- If you pour several matching pieces, type the count. Six posts means 6.
- Add waste, usually 5-10%, and any volume deductions.
- Click Calculate. 5×4×0.1 m and 5% give 2.1 m³. 10×0.4×0.5 m and 10% give 2.2 m³.
- Cement in the mix and mortar bags sit next door. This page stays concrete volume.
m³ of a 5 by 4 m slab 10 cm thick
Three sizes plus waste minus deductions. A 5 by 4 m slab 10 cm thick at 5% is 2.1 m³.
- m³
- Concrete to order. 5 × 4 × 0.1 × 1.05 = 2.1. A 10 by 0.4 by 0.5 m footing at 10% is 2.2 m³.
- cm
- Thickness 10 cm is typed as 0.1 m. Six 0.3×0.3×1 m posts at 5% are 0.567 m³, still in meters.
Usage examples
Example 2
- 10 × 0.4 × 0.5 m
- +10% waste
- 0 deductions
2.2 m³
With larger pours, even a modest waste allowance can change cost and delivery planning.
Example 3
- 0.3 × 0.3 × 1 m
- × 6
- +5% waste
0.567 m³
Shows why counting identical elements early helps when timing a pour.
Example 4
- 1.2 × 0.3 × 0.18 m
- × 12 steps
- +8% waste
≈ 0.84 m3
Twelve steps 1.2 × 0.3 × 0.18 m with 8% waste come to about 0.84 m3.
Example 5
- 8 × 1.2 × 0.1 m
- +5% waste
1.008 m3
A path 8 m by 1.2 m at 10 cm and 5% waste is 1.008 m3.
Example 6
- 6 × 0.4 × 0.4 m
- deduct 0.05 m3
- +5%
0.958 m3
After 5% waste and subtracting 0.05 m3 for a pipe, the result is 0.958 m3.
Example 7
- 6 × 5 × 0.12 m
- +7% waste
3.852 m3
A 6 × 5 m garage slab at 12 cm and 7% waste is 3.852 m3, under one 6 m3 truck.
Example 8
- 1 × 1 × 0.4 m
- × 2
- +10% waste
0.88 m3
Two footings 1 × 1 × 0.4 m with 10% waste give 0.88 m3, not 0.80 m3 dry.
Related calculators
Frequently asked questions
How much concrete for a 5×4×0.1 m slab at 5% waste?
2.1 m³. 5×4×0.1 alone is 2.0 m³; waste adds 0.1 m³.
How much concrete for a 10×0.4×0.5 m footing at 10%?
2.2 m³. Without waste the prism is 2.0 m³, then 10% reserve lifts it.
How much concrete for 6 posts 0.3×0.3×1 m at 5%?
0.567 m³. One post is 0.09 m³, six are 0.54, plus 5%.
How do I type a 10 cm thickness?
As 0.1 m. Typing 10 in a meter field would be a hundred times too much.
How much concrete for 12 treads 1.2×0.3×0.18 m at 8%?
About 0.84 m³. The count multiplies one tread, then waste goes in.
Are deductions subtracted before waste?
The calculator multiplies sizes and waste, then subtracts deducted volume. The result does not go below zero.
Where do I count cement for this volume?
On cement in mortar or on mortar bags. This page stays m³ of concrete.
What waste should I add to a slab?
Usually 5-10%. A 2 m³ slab at 5% is 2.1 m³. An uneven base sits closer to 10%.
Does an empty element count mean zero pours?
An empty count means one element. A typed zero zeros the volume.
How many m³ for a 20 m² patio 10 cm thick at 5%?
20 × 0.1 × 1.05 = 2.1 m³, the same order as a 5 by 4 m slab.
Knowledge sources
Volume and waste come from the sizes you type. Below are volume and NIST SI units.
Page updated in 2026.