By Sam Alex, civil engineer · About the author
Most renovation trips back to the hardware store happen because someone measured for one material, then had to guess for the next. With a tape measure, a notepad and ten minutes, you can take one set of measurements that gives you every quantity for a room. Here's how I do it, with a worked example.
What to measure
Draw a quick plan of the room (it doesn't need to be to scale), then write these on it in metres: 1. Length and width of the floor, wall to wall 2. Ceiling height 3. Each door: width × height 4. Each window: width × height 5. Anything unusual: a bay window, a bulkhead, built-in cupboards, a fireplace
Measure at floor level for floors, and at a few heights for walls. Older houses are rarely perfectly square.
The example room
A bedroom 4.0 m × 3.5 m with a 2.4 m ceiling, one door (0.82 × 2.04 m) and one window (1.8 × 1.2 m).
Floor area → flooring and tiles
- Floor area: 4.0 × 3.5 = 14.0 m²
- Laminate or vinyl plank with 7% waste: 14.0 × 1.07 = 15.0 m² to buy, then divide by the pack coverage and round up
- Tiles with 10% waste: 14.0 × 1.10 = 15.4 m². For 600 × 600 tiles, that's 15.4 ÷ 0.36 = 42.8, so 43 tiles
The flooring calculator and tile calculator do the arithmetic, including rounding up to whole units.
Perimeter → skirting and trims
- Perimeter: 4.0 + 3.5 + 4.0 + 3.5 = 15.0 m
- Less the doorway: 15.0 − 0.82 = 14.2 m of skirting
- Skirting comes in fixed lengths (often 5.4 m), and you lose some to mitres, so buy 3 lengths (16.2 m)
Wall area → paint
- Gross wall area: perimeter × height = 15.0 × 2.4 = 36.0 m²
- Less the door (1.67 m²) and window (2.16 m²): 32.2 m²
- Two coats: 64.4 m²
- At 12 m² per litre: 64.4 ÷ 12 = 5.4 L, so buy 6 L (for example, a 4 L tin plus a 2 L tin)
The paint calculator will add a waste allowance for you.
Ceiling area → ceiling paint or plasterboard
- Ceiling: same as the floor, 14.0 m²
- Two coats of ceiling paint at 12 m²/L: 28 ÷ 12 ≈ 2.3 L
- If re-sheeting: 14.0 ÷ 2.88 m² per 2400 × 1200 sheet = 4.9, so 5 sheets (or fewer, longer sheets to avoid joins)
Wall area again → wallpaper or wall tiles
For a feature wall 4.0 m wide: 4.0 × 2.4 = 9.6 m². Standard rolls cover 5.3 m² (0.53 × 10.05 m). With 15% waste for pattern matching, that's 2.1, so 3 rolls. The wallpaper calculator and drop counting both give the same answer.
Tips that save money
- Keep your sketch. Photograph it with your phone so it's with you in the store.
- Buy all of one product at once from the same batch. Colours vary between batches of paint, tiles, flooring and wallpaper.
- Keep leftovers. A spare box of tiles or a litre of paint makes future repairs invisible.
- Measure twice where it's expensive. Stone benchtops and custom joinery need a professional check measure anyway.
Frequently asked questions
Should I subtract windows and doors when calculating paint?
Yes, for large openings. Small ones make little difference, and the extra paint becomes your touch-up supply.
How much extra flooring should I buy?
Typically 5–10% for straight layouts and 15–20% for herringbone or diagonal patterns.
What is the quickest way to measure a room?
A laser measure is fastest and works well alone. Take each measurement twice, and at more than one height for walls.