Walls, Flooring & Finishes Calculators (Tile, Paint & Plaster)

Wall, Flooring & Finishes Calculators — Tile, Paint & Plaster

Use these free calculators for wall area, tile, flooring, paint, plaster and accent walls. Enter your measurements, get instant quantities.

• 6 calculators
• Metric & imperial
• Waste calculator built in
• Free, no sign-up

Browse the calculators How we calculate

What are you calculating?

Pick the surface or finish you're working on and jump straight to the right calculator.

Wall
Area Tile
Calculation Flooring
Calculation Paint
Calculation Plaster
Calculation Accent
Wall

All 6 calculators

Every calculator works from the measurements you already have on site. Enter your numbers, review the result, then add a waste allowance before ordering tiles, flooring, paint or plaster.

01

Wall Area Calculator

Measure total wall surface area, deduct doors and windows, and get the net painted or plastered area for any room.

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02

Tile Calculator

Work out how many tiles and boxes you need for floors, walls or wet areas, including waste for cutting and pattern layout.

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03

Flooring Calculator

Calculate floor area and convert to boxes of laminate, vinyl planks or engineered wood — waste included.

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04

Paint Calculator

Estimate litres or gallons of paint per room per coat, based on wall area and manufacturer coverage rates.

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05

Plaster Calculator

Work out plaster, sand and cement quantities for a given wall area and thickness, plus bags of ready-mixed plaster.

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06

Accent Wall Calculator

Measure one wall's surface and estimate its paint, panelling or wallpaper coverage with a waste allowance.

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How wall, floor & finish calculations work

Every tool reduces a physical measurement to one formula. Understanding the formula lets you verify a supplier's quote and spot an under-order before it costs you a second trip.

Wall area (net of openings)

Perimeter × ceiling height gives gross wall area. Subtract doors and windows to get the net painted or plastered area.

Net wall area = (Perimeter × Height) − Openings

A 4 × 5 m room with 2.5 m walls has 45 m² gross; a 2 m² door and a 1.5 m² window bring it to 41.5 m² net.

Tiles per square metre

Divide 1 m² by the area of a single tile (in m²). Add a waste factor that depends on cutting, layout and pattern.

Tiles per m² = 1 ÷ (tile length × tile width)

A 300 × 300 mm tile covers 0.09 m², so you need 11.11 tiles per m². A 300 × 600 mm tile needs 5.56 tiles per m².

Paint coverage per litre

Most interior emulsions cover 10–12 m² per litre on a smooth, sealed wall in one coat. Rough or textured walls drop to 6–8 m² per litre.

Litres = (Wall area × Coats) ÷ Coverage rate

A 45 m² wall at two coats and 11 m² per litre needs 8.18 L. Round up to the nearest 2.5 L or 5 L tin.

Plaster per square metre

Ready-mixed plaster covers about 1.1 m² per kg at 10 mm thickness. Sand-and-cement render needs roughly 0.02 m³ of mixed mortar per m² at 12 mm.

Plaster kg = Area × Thickness ÷ Coverage per kg

A 45 m² wall at 10 mm thickness needs ~40 kg of ready-mixed plaster (45 ÷ 1.1).

Note on waste factors. Wall finishes need more waste than floors. A straight wall with standard tile takes 5–10% waste; a bathroom with cut-outs around fixtures needs 10–15%; a herringbone or chevron pattern needs 15–20%. Floors in rectangular rooms typically need only 5–8%.

Worked example: 4 × 5 m living room, fully finished

A step-by-step calculation from raw measurements to material order. Every figure below comes from the calculators on this page.

Step	Calculation	Result
1. Floor area	4 × 5	20 m²
2. Wall perimeter	2 × (4 + 5)	18 m
3. Gross wall area (2.5 m ceiling)	18 × 2.5	45 m²
4. Deduct door (0.9 × 2.1) and window (1.5 × 1.2)	45 − 1.89 − 1.8	41.31 m² net
5. Paint (2 coats, 11 m²/L)	41.31 × 2 ÷ 11	7.51 L → order 10 L
6. Floor tiles (300 × 300 mm)	20 ÷ 0.09 = 222.2 tiles × 1.10 waste	244 tiles → 27 boxes of 9
7. Skirting board (perimeter − door)	18 − 0.9	17.1 m → 4 × 4.2 m lengths
8. Plaster (10 mm, ready-mixed)	41.31 ÷ 1.1	~37.6 kg → 2 × 25 kg bags

Coverage quick reference

Standard tile counts and paint coverage rates used across residential work. These numbers drive every calculator on this page — check them against your product data sheet before ordering.

Tile size	Tile area (m²)	Tiles per m²	Common application
100 × 100 mm	0.010	100.0	Small bathroom walls, mosaic
200 × 200 mm	0.040	25.0	Kitchen splashbacks, utility floors
300 × 300 mm	0.090	11.11	General floors, bathrooms
300 × 600 mm	0.180	5.56	Wall tiles, wet rooms
600 × 600 mm	0.360	2.78	Large format floors, living areas
600 × 1200 mm	0.720	1.39	Modern large format porcelain

Surface / product	Coverage	Unit	Notes
Interior emulsion (1 coat)	10–12	m² per litre	Smooth, sealed plaster. Drops to 6–8 on texture.
Exterior masonry paint	4–6	m² per litre	Rough render reduces coverage.
Primer / undercoat	12–14	m² per litre	Higher than topcoat on sealed surfaces.
Ready-mixed plaster (10 mm)	1.0–1.2	m² per kg	Bag of 25 kg covers ~27 m² at 10 mm.
Thistle Multi-Finish (UK)	~1.1	m² per kg	Two-coat system, 3–5 mm total.
Sand-and-cement render (12 mm)	0.02	m³ per m²	Ratio 1:4 or 1:5.

Wall, tile and paint standards by country

Tile sizes, paint coverage and finishing specs differ between the US, UK, Australia and New Zealand. The formulas stay the same — only the input numbers move.

Region	Tile sizing	Paint coverage	Typical waste factor
United States	Inches (4×4, 6×6, 12×12, 12×24)	sq ft per gallon (~350–400)	10% tiles, 10% paint
Canada	Mixed — metric for tile, imperial for paint	sq ft per gallon or m² per litre	10–15% tiles
United Kingdom	Millimetres (100×100, 300×300, 300×600, 600×600)	m² per litre (~10–12 interior)	10% tiles, 5–10% paint
Australia & NZ	Millimetres, larger formats dominate	m² per litre	10–15% tiles, 10% paint

How to choose the right wall, floor or finish calculator

Each calculator answers one question. Start with the measurement you already have, not the one you think you need.

You know the room dimensions and want wall area

Use the Wall Area Calculator. Enter the room's length, width and ceiling height, then deduct doors and windows. The result feeds directly into the paint, plaster and wallpaper calculators.

You're tiling a floor or wall

Use the Tile Calculator. It takes surface area and tile dimensions, then returns the exact tile count, boxes and adhesive. Add 10% waste for straight layout, 15% for diagonal, 20% for herringbone.

You're laying laminate or engineered wood

Use the Flooring Calculator. Give it room dimensions and plank size, and it returns pack count and underlayment area. Add 5–8% waste for rectangular rooms, 10% for L-shaped or angled areas.

You're painting a room

Use the Paint Calculator. It multiplies wall area by the number of coats, divides by the paint's coverage rate, and returns litres or gallons — plus primer if the wall is new plaster.

You're plastering or rendering

Use the Plaster Calculator. Enter area and finish thickness — it returns ready-mixed bag counts, or sand and cement volume for render. Remember that two coats mean double the material.

You're designing a feature wall

Use the Accent Wall Calculator. It treats one wall as a standalone surface and estimates paint, panelling or wallpaper with the correct waste factor for a feature finish.

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Walls, flooring & finishes FAQs

How do I calculate the wall area of a room for painting?

Multiply the room's perimeter by the ceiling height to get gross wall area, then subtract the area of doors and windows. For a 4 × 5 m room with a 2.5 m ceiling, gross area is (4 + 5) × 2 × 2.5 = 45 m². Subtracting one door (1.9 m²) and one window (1.8 m²) leaves 41.3 m² net. The Wall Area Calculator does this in one step.

How many tiles do I need per square metre?

Divide 1 m² by the area of a single tile in m². A 300 × 300 mm tile covers 0.09 m², so you need 11.11 tiles per m². A 600 × 600 mm tile covers 0.36 m², so you need 2.78 tiles per m². Then multiply by the total area and add waste — 10% for straight layouts, 15% for diagonal, 20% for herringbone.

How much paint do I need for one room?

Multiply net wall area by the number of coats, then divide by the paint's coverage rate. Most interior emulsion covers 10–12 m² per litre in one coat. A 41 m² wall at two coats needs roughly 41 × 2 ÷ 11 = 7.5 L — round up to the nearest tin (10 L is common).

How much waste should I add for tiles and flooring?

Tiles: 10% for a straight grid layout on a rectangular wall, 15% for diagonal or staggered layouts, and 20% for herringbone or chevron. Flooring: 5–8% for rectangular rooms, 10% for L-shaped or angled rooms, 15% for complex layouts with many cut-outs.

What is the difference between wall area and floor area?

Floor area is length × width — one flat surface. Wall area is perimeter × height — the four vertical surfaces combined. For a 4 × 5 m room with 2.5 m ceilings: floor area is 20 m², gross wall area is 45 m².

How much plaster do I need per square metre?

Ready-mixed plaster covers about 1.0–1.2 m² per kg at 10 mm thickness. A 25 kg bag covers roughly 25–30 m². Sand-and-cement render at 12 mm thickness needs about 0.02 m³ of mortar per m², which is roughly 20 kg of dry mix per m² (1:4 ratio).

How do I calculate how many boxes of flooring to buy?

Divide the total floor area plus waste by the coverage of one box (usually printed on the packaging, often 1.5–2.5 m² per box). A 20 m² room with 8% waste needs 21.6 m² of flooring. If each box covers 2.2 m², you need 10 boxes (21.6 ÷ 2.2 = 9.82, rounded up).

Does paint coverage change on new plaster?

Yes — significantly. New plaster absorbs paint fast, so coverage drops from 10–12 m²/L to 6–8 m²/L on the first coat. A mist coat (thinned primer, roughly 1 part water to 4 parts paint) is required before topcoat. Add 25–30% more paint to your estimate for new plaster.

How do I calculate accent wall materials?

Treat the accent wall as one standalone surface — just length × height, minus any openings. Use the Accent Wall Calculator for paint, wallpaper or panelling. Waste is lower than a full-room job because there's only one plane to cover, but patterns still need 15–20% waste.

Are wall and flooring calculator results exact?

No — they're estimates based on the measurements and waste factors you enter. Real quantities vary with cutting, breakage, pattern matching, surface irregularity, product packaging and site conditions. Always verify against the material supplier's coverage data before ordering, and keep a spare box or tin for future repairs.

Do I need different waste factors for exterior vs interior walls?

Yes. Interior walls are typically flatter and more consistent, so 5–10% waste on tiles and paint is normal. Exterior walls with rough render, external corners and window reveals need 10–15% on tiles and 15% on paint, because more material is lost to absorbency and cutting.

Can I use these calculators in metric and imperial units?

Yes. Every calculator accepts both metric (m, m², kg, L) and imperial (ft, ft², lb, gal) input, and returns results in the unit you select. If your supplier quotes in a different system, convert before comparing prices — the Construction Unit Converter handles length, area, volume and weight in one step.

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