How to Measure for Tile, Flooring, and Paint Using Your iPhone
A practical guide to converting room dimensions into material quantities, with the exact waste factors, pattern adjustments, and unit conversions for tile, flooring, paint, and wallpaper.
Knowing a room is 18 m² doesn't tell you how many boxes of tile to buy. Manufacturers package materials in inconvenient units (rectangular tiles in m², round paint in litres, wallpaper in 2.6 m × 0.5 m rolls), and every material has a waste factor that varies by how complicated your room shape is. Here's the math, and how the app does it for you.
Step 1: Get the right base measurement
For each material, you need a different baseline number:
| Material | What to measure |
|---|---|
| Floor tile / laminate / vinyl | Floor area (m²) |
| Wall tile | Tiled wall area minus fixtures (m²) |
| Paint (walls) | Wall area minus door + window cutouts (m²) |
| Paint (ceiling) | Ceiling area = floor area (m²) |
| Wallpaper | Wall area minus cutouts (m²) |
| Baseboard / skirting | Floor perimeter minus door widths (m) |
| Crown moulding | Ceiling perimeter (m) |
Ruler AR's room scan gives you floor area and floor perimeter automatically. Wall area requires a small calculation: wall perimeter × ceiling height − sum of door areas − sum of window areas. The material calculator in the app does this for you.
Step 2: Apply the right waste factor
"Waste" is the material you'll cut off, drop, mismatch, or have defects in. Add this percentage to your base quantity:
| Scenario | Waste factor |
|---|---|
| Square room, large-format tile (60×60 cm) | +10% |
| Standard tile (30×30 cm) | +10-15% |
| Small tile / mosaic | +15-20% |
| Diagonal pattern | +15% |
| Herringbone / chevron | +20% |
| Laminate / vinyl plank | +10% (straight lay) |
| Carpet | +10-15% (depends on roll width vs room) |
| Wallpaper with pattern repeat | +15-20% |
| Solid-colour paint | +5-10% (touch-ups, second coat) |
Add another 5% for irregularly-shaped rooms (alcoves, columns, non-rectangular footprint), those generate more cuts.
Step 3: Convert to manufacturer's units
Manufacturers don't sell in m². They sell in boxes, tins, rolls. Convert:
Tile
(Floor area × (1 + waste factor)) ÷ tile size = tiles needed → round up to whole boxes.
Example: 18 m² floor + 10% = 19.8 m². Tile size 60×60 cm = 0.36 m². 19.8 ÷ 0.36 = 55 tiles. Box of 6 = 10 boxes (rounded up from 9.17).
Laminate / vinyl plank
Same as tile, except boxes are typically labelled with coverage in m². Floor 18 m² + 10% = 19.8 m². Box covers 2.4 m². Need 9 boxes.
Paint (walls)
Wall area × number of coats ÷ coverage = litres needed.
Typical coverage: 10 m² per litre for one coat. Two coats is standard for fresh painting.
Example: 50 m² wall area × 2 coats ÷ 10 m²/L = 10 L. Sold in 5 L tins → 2 tins.
Wallpaper
Wall area ÷ roll coverage + 10-20% for pattern match. Standard roll = 5 m² coverage (10.05 m × 0.53 m). Pattern-repeat rolls need additional length for matching.
Example: 30 m² wall area + 15% pattern = 34.5 m² ÷ 5 m²/roll = 7 rolls (rounded up from 6.9).
The material calculator inside the app
Once you have a saved room project in Ruler AR, the material calculator does all of the above automatically:
- Open the saved room project.
- Tap Material Calculator.
- Choose a material: paint, floor tile, wallpaper, etc.
- Adjust waste factor if your room is non-standard.
- Pick a unit size (e.g. tile size 30×30 vs 60×60, paint tin 1 L vs 5 L).
- The app outputs both the quantity in m² and the rounded-up package count.
Export the estimate as part of the room's PDF and take it to the hardware store. The PDF doubles as your shopping list.
Pricing the materials
With your quantities in hand, browse 2-3 retailers for unit prices. For each:
- Multiply unit price × packages needed = line cost
- Add delivery if not local pickup
- Total for that retailer = comparison number
Hardware retail prices vary by 30-50% on identical products between IKEA, Home Depot/Lowe's, Leroy Merlin, B&Q, etc. The 10 minutes of comparison shopping with measured numbers usually saves €50-200 on a kitchen-sized renovation.
Common mistakes
- Forgetting waste factor. Buying exactly the room area is the #1 reason for second supply runs.
- Wrong unit conversion. US (gallons) ↔ EU (litres), US (sq ft) ↔ EU (m²). The app converts; doing it by hand introduces errors.
- Mismatched dye lots. Tile and paint from different production batches can look subtly different. Buy slightly more than you need from one lot rather than coming back for more later.
- Including unusable areas. Don't tile under the kitchen island if it's permanent. Don't paint behind built-in wardrobes.
Bottom line
Measuring the room is the easy part. Converting m² into "how many boxes" is where most DIY budgets blow. With a measured floor plan in Ruler AR plus the in-app material calculator, you get per-material quantities in 30 seconds, accurate enough to shop confidently without buying twice.