Construction Material Calculator
Paint, tiles, concrete and bricks for a room or a wall.
Last updated
Your details
Result
- Paint needed
- 14.80 litres
- Wall area
- 54.00 m²
- Ceiling area
- 20.00 m²
- Walls only
- 10.80 litres
Buy 15 L to allow for touch-ups
Related calculators
Formula — written step by step
Paint, for a 5 × 4 m room…
Litres = (wall area + ceiling) ÷ coverage × coats
Walls = 2 × (5 + 4) × 3 = 54 m²
Ceiling = 5 × 4 = 20 m²
Litres = (54 + 20) ÷ 10 × 2
Litres = 74 ÷ 10 × 2
Litres = 14.8
Coverage is the square metres one litre covers in a single coat — 10 m² is typical for a smooth, previously painted wall. Openings are not deducted, so subtract large windows and doors before buying.
Tiles, for a 5 × 4 m floor…
Tiles = floor area ÷ tile area × (1 + waste)
Floor = 5 × 4 = 20 m²
One tile = 0.6 × 0.6 = 0.36 m²
Tiles = 20 ÷ 0.36 = 55.6
With 10% waste: 55.6 × 1.10 = 61.1
Tiles = 62, rounding up
Tile sizes are entered in centimetres because that is how they are sold, and converted to metres before dividing. The count always rounds up — most of a tile is no use.
Concrete, for a 5 × 4 m slab…
V = length × width × depth × (1 + waste)
V = 5 × 4 × 0.15
V = 3 m³
With 10% waste: 3 × 1.10
V = 3.3 m³
Depth is the slab thickness in metres, so 150 mm is entered as 0.15. The cement, sand and aggregate figures come from that volume multiplied by 1.54, the dry-volume factor: dry materials compact once water is added.
Bricks, for a 5 × 3 m wall…
Bricks = (length × height × thickness) ÷ 0.002 × (1 + waste)
Wall = 5 × 3 × 0.1 = 1.5 m³
One brick with its joint = 0.2 × 0.1 × 0.1 = 0.002 m³
Bricks = 1.5 ÷ 0.002 = 750
With 10% waste: 750 × 1.10
Bricks = 825
The brick is sized with its mortar joint included — 190 mm of brick plus a 10 mm joint is 200 mm. Using the bare brick size would under-order by about 15%.
The formula for each shape
-
Paint
L = (2(l + w)h + lw) ÷ coverage × coats
Needs room length, width, wall height, coverage, coats · answer in litres
-
Floor tiles
N = floor area ÷ tile area × (1 + waste)
Needs floor length and width, tile size, wastage · answer in tiles
-
Concrete
V = l × w × depth × (1 + waste)
Needs slab length, width and depth, wastage · answer in m³
-
Bricks
N = (l × h × t) ÷ 0.002 × (1 + waste)
Needs wall length, height and thickness, wastage · answer in bricks
A worked example
Concrete for a 5 × 4 m slab
- Length
- 5 m
- Width
- 4 m
- Depth
- 0.15 m
- Wastage
- 10%
- V = length × width × depth
- V = 5 × 4 × 0.15
- V = 3 m³
- With 10% wastage: 3 × 1.10
V = 3.3 m³ of concrete
The cement, sand and aggregate figures come from that volume multiplied by 1.54, the dry-volume factor: dry materials compact when water is added, so you must batch more than the finished volume.
Bricks for a 5 × 3 m wall
- Wall length
- 5 m
- Wall height
- 3 m
- Thickness
- 0.1 m
- Wastage
- 10%
- Wall volume = 5 × 3 × 0.1 = 1.5 m³
- One brick with its joint = 0.2 × 0.1 × 0.1 = 0.002 m³
- Bricks = 1.5 ÷ 0.002 = 750
- With 10% wastage: 750 × 1.10
825 bricks
The brick is sized with its mortar joint included — 190 mm of brick plus a 10 mm joint is 200 mm. Using the bare brick size would under-order by about 15%.
How to use this calculator
- Pick what you are estimating. The drawing and the fields both change to match, so you are only ever asked for measurements that job actually needs.
- Measure in metres. Tile sizes are the exception and are entered in centimetres, as they are sold.
- Set a wastage allowance: 10% suits tiles and brickwork, 5% a simple concrete pour. Raise it for diagonal tile patterns or an awkward layout.
- Enter a price per unit if you want a cost. Leave it blank and the calculator reports quantities only.
- Round up when ordering, and buy tiles from a single batch — colour drifts between production runs.
Always buy more than the calculation says
These figures are theoretical volumes. Real sites lose material to cuts, spillage, breakage and mistakes, which is why a wastage allowance of 10% is standard for tiles and 5% for concrete — more for complex layouts or diagonal tile patterns.
For tiles specifically, buy from a single batch. Colour varies subtly between production runs, so a replacement bought a year later will rarely match.
Paint coverage varies more than the tin admits
The 10 m² per litre default suits a smooth, previously painted wall. Bare plaster, textured render and porous masonry can drop that to 6 m² or less on the first coat, and dark-to-light colour changes often need three coats rather than two.
Windows and doors are not deducted here. On a room with large openings, subtract their area from the wall figure before buying.
Formula & methodology
What this calculator assumes
- Paint coverage of about 10–12 m² per litre per coat is the typical manufacturer figure for a smooth, previously painted surface. Bare plaster, masonry and textured surfaces absorb considerably more.
- A wastage allowance is applied because cuts, breakages and off-cuts are unavoidable. Ten percent is the usual trade figure; diagonal or patterned tile layouts need more.
- Brick counts assume a standard mortar joint. Changing the joint thickness changes the count per square metre appreciably.
- Concrete volume is the finished volume and excludes over-dig, formwork deflection and any sub-base.
Sources
- Chudley & Greeno, Building Construction Handbook, 12th edition, Routledge, 2020 — material quantities and wastage allowances.
Typical allowances
| Job | Standard allowance | Raise it when |
|---|---|---|
| Floor tiles | 10% | Diagonal or herringbone layouts, many cuts, small rooms |
| Wall tiles | 10–15% | Patterned tiles that must line up across joints |
| Concrete | 5% | Uneven subgrade, or formwork that may bulge |
| Bricks | 5–10% | Site handling, or a wall with many openings to cut around |
| Paint | Buy the next whole tin | Bare plaster, dark-to-light changes, textured render |
These are ordering allowances, not safety factors. Structural concrete should follow an engineer's specified mix rather than the nominal 1:2:4 used here.
Frequently asked questions
What mix ratio does the concrete estimate use?
A nominal 1:2:4 by volume — one part cement, two sand, four aggregate — with a 1.54 dry-volume factor. Structural work should follow an engineer's specified mix, not a rule of thumb.
How much wastage is built into the tile estimate?
Around 10%, which suits a straightforward rectangular room. Diagonal layouts, large-format tiles and rooms with many cuts around fittings warrant 15% or more. Order the whole quantity in one batch: tile colour varies between production runs and a later top-up may not match.
Does the paint figure include a second coat?
The number of coats is yours to set, and two is the normal case. A colour change, a porous surface or bare plaster can absorb noticeably more on the first pass, so treat the first coat as the uncertain one and buy accordingly.
Can I use this for a structural quantity?
No. These are planning estimates for ordering material, not engineering quantities. Anything load-bearing needs a specified mix, a specified reinforcement schedule and a professional take-off, none of which a rule of thumb can supply.