Getting the measurements right before ordering flooring, tiles, paint, or wallpaper can save you a costly return trip to the shop — or worse, running out mid-project. This guide walks through how to measure common room shapes accurately, apply the right waste allowances for each material, and handle awkward rooms that don't fit a simple rectangle.
Basic Square Footage Formula
Area (sq ft) = Length (ft) × Width (ft)
Area (m²) = Length (m) × Width (m)
Conversion: 1 m² = 10.764 sq ft
In the UK, flooring and most materials are sold in square metres. If your measurements are in feet, convert first or use the conversion factor at the end.
Step-by-Step Room Measurement
- Clear the room as much as possible for accurate measurements.
- Measure at the widest points of the room, even if there are bay windows or recesses. Always measure from wall to wall, including any skirting boards.
- Measure to the nearest centimetre (or ¼ inch). Small errors multiply across large rooms.
- Sketch a floor plan — even a rough one — before calculating. Mark all measurements.
- Measure twice, order once. Always re-measure before placing your order.
L-Shaped Rooms
The most common irregular room shape. Divide it into two rectangles, measure each, and add:
Example: An L-shaped room with a living area 5 m × 4 m and a dining bay 2 m × 2.5 m:
- Rectangle 1: 5 × 4 = 20 m²
- Rectangle 2: 2 × 2.5 = 5 m²
- Total: 25 m²
Tip: When dividing, be careful not to double-count any area. Draw your dividing line clearly and measure each rectangle independently.
Material-Specific Waste Allowances
Never order the exact calculated area — every material requires a waste allowance for cutting, matching, and breakage.
| Material | Waste Allowance | Notes |
|---|---|---|
| Laminate / vinyl planks (straight lay) | +10% | More for rooms with many cuts |
| Laminate / vinyl planks (diagonal lay) | +15% | Diagonal increases cutting waste |
| Carpet | +10–15% | Depends on pile direction requirements |
| Square tiles (straight lay) | +10% | Allow more for small tiles |
| Square tiles (diagonal lay) | +15% | More edge cuts required |
| Wallpaper (plain) | +10% | Plus one extra roll as backup |
| Wallpaper (large repeat pattern) | +25–30% | Pattern matching wastes more paper |
| Paint | +0% | Paint is sold by coverage area — just add coats |
Flooring Example: Bedroom
Bedroom: 3.8 m × 3.2 m = 12.16 m². Laying diagonal laminate (+15%):
Order: 12.16 × 1.15 = 13.98 m² → Round up to 14 m².
If laminate comes in 1.5 m² packs: 14 ÷ 1.5 = 9.33 → order 10 packs.
Tiling Example: Bathroom
A bathroom has three walls to tile: Wall A (2.1 m × 2.4 m), Wall B (1.8 m × 2.4 m), and Wall C (2.1 m × 2.4 m). A window alcove of 0.9 m × 1.2 m in Wall C is not tiled.
- Wall A: 2.1 × 2.4 = 5.04 m²
- Wall B: 1.8 × 2.4 = 4.32 m²
- Wall C: (2.1 × 2.4) − (0.9 × 1.2) = 5.04 − 1.08 = 3.96 m²
- Total: 5.04 + 4.32 + 3.96 = 13.32 m²
- Add 10% waste: 13.32 × 1.10 = 14.65 m² → order 15 m²
Paint Calculator
Paint coverage varies by product and surface, but a standard emulsion covers approximately 10–12 m² per litre (smooth surfaces), or 8–10 m² (textured/first coat). For wall area:
Wall area = (Room perimeter × Ceiling height) − (Doors + Windows)
Standard door: 1.9 m² | Standard window: 1.5 m²
Example: A 4 m × 3.5 m room with 2.4 m ceilings, 1 door, 2 windows:
Perimeter = 2 × (4 + 3.5) = 15 m
Gross wall area = 15 × 2.4 = 36 m²
Subtract: 36 − 1.9 − (2 × 1.5) = 36 − 4.9 = 31.1 m²
For 2 coats at 10 m²/litre: (31.1 × 2) ÷ 10 = 6.22 litres → buy two 3.5L tins
Converting Between sq ft and m²
Some US-based products and older UK property listings use square feet:
- m² to sq ft: × 10.764
- sq ft to m²: × 0.0929
100 sq ft = 9.29 m² | 200 sq ft = 18.58 m² | 500 sq ft = 46.45 m²
Summary
Measure to the nearest centimetre at the widest points. For L-shaped rooms, split into rectangles and add. Always add waste: 10–15% for flooring, 10–15% for tiles, 25–30% for patterned wallpaper. Calculate wall paint area from perimeter × height, minus doors and windows. Use our square footage calculator to get instant results and material estimates.