Brazil Roof Tile Calculator (2026)
Data verified on
Enter the area your roof covers, its slope in percent and the tile type to find out how many pieces to buy. The calculator corrects the flat footprint by the slope factor — the mistake that leaves most self-builders short of tiles — applies manufacturer datasheet yields, and adds a waste margin for breakage and cutting.
Footprint versus actual roof surface
A floor plan gives you the projected area: the shadow the roof casts on the ground, eaves included. But roof planes are inclined, and an inclined plane always has more surface than its horizontal projection. Ordering tiles from the plan area guarantees a shortfall.
The correction is trigonometry. For a slope of i percent, the plane sits at θ = arctan(i/100) from horizontal, and the real surface equals the footprint divided by cos(θ) — which is the same as multiplying by the square root of 1 + (i/100)².
A 100 m² footprint at 30% slope has a factor of 1.0440, giving 104.40 m² of actual tiled surface. On a large roof with a steep pitch the gap easily exceeds 10%.
| Slope | Approximate angle | Slope factor | Real surface for a 100 m² footprint |
|---|---|---|---|
| 10% | 5.7° | 1.0050 | 100.50 m² |
| 20% | 11.3° | 1.0198 | 101.98 m² |
| 30% | 16.7° | 1.0440 | 104.40 m² |
| 40% | 21.8° | 1.0770 | 107.70 m² |
| 50% | 26.6° | 1.1180 | 111.80 m² |
| 100% | 45.0° | 1.4142 | 141.42 m² |
Tiles per square meter and minimum slopes
Yield is the number of pieces needed to cover one square meter of actual roof surface. It varies with the model and the manufacturer, because the batten spacing — how far each tile overlaps the one below — is set by each factory.
Minimum slope matters even more than yield. Below it, water creeps between the pieces by capillary action and the roof leaks whenever rain arrives with wind. No tile compensates for the wrong pitch.
| Tile type | Pieces per m² | Usual minimum slope | Note |
|---|---|---|---|
| Portuguese clay tile | 17 | 30% | Interlocking brands such as Isotec specify 35% |
| Roman clay tile | 16.3 | 30% | Isotec and Montreal datasheets state 35% |
| French (Marseille) clay tile | 16 | 30% | NBR 8039 allows 25% to 36% |
| Corrugated fiber-cement 5 mm (2.44 × 1.10 m) | 0.414 sheet | 17.6% (10°) | 6 mm and 8 mm sheets go down to 8.7% (5°) with special care |
Where the fiber-cement figure comes from
A corrugated sheet does not cover its nominal area. A 2.44 × 1.10 m sheet measures 2.68 m² on paper, but the overlaps eat into it.
Brasilit’s technical catalog gives a useful width of 1.05 m (total width is 1.10 m; the difference is the quarter-corrugation side lap) and a minimum end lap of 14 cm for slopes between 15° and 75°.
So the useful length is 2.44 − 0.14 = 2.30 m and the useful area is 2.30 × 1.05 = 2.415 m². Dividing 1 by 2.415 gives 0.414 sheets per square meter — one sheet every 2.42 m². For a real roof surface of 104.40 m², that is 44 sheets before waste.
Worked example and a note on roof framing
For a 100 m² footprint at 30% slope with Portuguese clay tiles and 10% waste: the slope factor is 1.0440, giving 104.40 m² of real surface; at 17 tiles/m² that is 1,775 tiles, and with 10% waste you should buy 1,953. The same roof would need roughly 1,872 Roman tiles, 1,838 French tiles or 48 fiber-cement sheets.
Roof framing is deliberately not calculated here. Batten spacing follows each tile maker’s datasheet, the maximum purlin span for fiber-cement depends on sheet thickness, and sizing rafters and trusses requires the dead load, the regional wind load and the span — a structural engineering calculation. For reference, wet clay tiles weigh around 45 kg/m² against 16 kg/m² for a 5 mm fiber-cement sheet, so swapping one for the other changes the framing requirement entirely.
Frequently asked questions
How many roof tiles do I need per square meter?
Manufacturer datasheets give 17 pieces/m² for Portuguese clay tiles, 16.3 for Roman and 16 for French (Marseille). A 2.44 × 1.10 m corrugated fiber-cement sheet yields 0.414 sheets/m², so one sheet covers about 2.42 m². These figures apply to the actual sloped surface, not the floor-plan footprint.
How do I convert roof slope from percent to degrees?
The angle equals arctan(slope ÷ 100). A 30% slope is about 16.7°, 40% is 21.8°, and 100% is exactly 45°. Percent expresses the vertical rise per 100 units of horizontal run, which is why 100% is not vertical.
What is the minimum slope for clay roof tiles?
The usual market minimum is 30% for Portuguese, Roman and colonial tiles, though several interlocking-tile manufacturers specify 35% on their datasheets. Brazilian standard NBR 8039, which covers French-type tiles, works within a 25% to 36% range. Always check the datasheet for the exact model before building the framing.
Why add 5% or 10% for waste?
Because not every tile delivered becomes roof. Pieces break in transit and unloading, hips, valleys and eaves require cuts, and it pays to keep spares — tiles from different production batches vary in color. Use 5% on a simple two-sided roof and 10% when there are multiple planes, hips and valleys.
Sources
Estimate based on yields and minimum slopes published in manufacturer datasheets (Cerâmica Isotec, Cerâmica Montreal, Brasilit) and Brazilian standard ABNT NBR 8039. Yields and batten spacing vary by manufacturer and batch. Confirm the figures on the datasheet for the product you buy, and consult an engineer for roof framing design.
Related calculators
Also available in Portuguese: Calculadora de Telhado: Quantas Telhas por m²