The formula to calculate roof tile quantity = Roof Area (m²) × Pieces per m² × 1.05 (5% waste factor). The roof area is calculated from Building Area ÷ cos(roof pitch angle) for a gable roof. The pieces-per-m² value varies depending on tile type and the manufacturer’s mold size — always ask your supplier for the exact number before ordering.
Base Formula
Quantity = Roof Area × Pieces per m² × Waste FactorStep-by-Step Calculation
Step 1: Calculate the Roof Area
Gable roof (most common):
Roof area = Building area ÷ cos(pitch angle)Example: Building area 60 m², pitch 30°
→ 60 ÷ cos(30°) = 60 ÷ 0.866 = 69.3 m²
Hip roof (pyramid):
Roof area = Building area × factor 1.15–1.25 (depending on pitch)Complex roof (multiple valleys):
Calculate each face separately, then sum them.
Step 2: Determine Pieces per m²
Important note: pieces per m² varies between manufacturers depending on mold size and tile shape (flat, wave, etc.). Always confirm with your supplier before the final calculation. As a rough guide, concrete tiles typically require around 9–13 pieces per m² depending on type.
Step 3: Add a Waste Factor
| Roof Type | Waste Factor | Multiplier |
|---|---|---|
| Simple gable | 5% | ×1.05 |
| Standard hip | 8–10% | ×1.08–1.10 |
| Complex / many valleys | 10–12% | ×1.10–1.12 |
Worked Examples (Using 11 pcs/m² Assumption)
The 11 pcs/m² figure below is an example assumption — not an absolute rule. Use the actual figure from your supplier.
Type 45 House (Gable Roof, 30° Pitch)
- Building area: 45 m²
- Roof area = 45 ÷ 0.866 = 52 m²
- At 11 pcs/m²: 52 × 11 = 572 pcs
- Add 5% waste: 572 × 1.05 = ≈ 601 pcs
Type 70 House (Hip Roof, 35° Pitch)
- Building area: 70 m²
- Roof area = 70 × 1.20 = 84 m²
- At 11 pcs/m²: 84 × 11 = 924 pcs
- Add 10% waste: 924 × 1.10 = ≈ 1,017 pcs
Don’t Forget Accessories
- Ridge tiles: roof length ÷ effective width per ridge tile
- End ridges: typically 2 pcs per side
- T-junctions: for hip roofs with valleys
- Battens & rafters: as required by the roof frame structure
Tips to Avoid Shortages
- Order 5–10% extra beyond the accurate estimate
- Keep spares for future replacements
- Order a single batch for color consistency
- Confirm tile dimensions before ordering (varies between makers)
- Ask the supplier to help with the calculation — often free
Need a consultation for your roofing project? Contact Genteng UI (PT Karya Mulia Permai) — our team is ready to help you estimate tile quantities for your project.
WhatsApp: +62 811-3019-898
Email: [email protected]
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