Trade & Construction

Roofing Calculator

Trade & Construction

Roofing Calculator

Roof order first

Instant roofing order25 packs72.82 m2 order area from 66.2 m2 sloped roof area.

72.82 m2Order area66.2 m2Sloped roof1.1034Pitch factor10%Waste

Formula: plan area x pitch factor x (1 + waste) / pack coverage, rounded up. Add ridge, valley, flashing, underlay, fixings and safety/access separately.

10 m x 6 m plan25 deg pitch3 m2/pack

Plan length (m)Horizontal building or roof-plan length, not slope length.Plan width (m)Horizontal roof-plan width across both sides for a simple gable roof.

Waste and pack basis

Roof pitch (degrees)Pitch angle above horizontal. The calculator uses cosine to convert plan area to sloped area.Waste allowance (%)Coverage per pack (m²)Use bundle, sheet, roll or pack coverage from the supplier.

Live result66.2 m²order area 72.82 m² · 25 packs

Formula used

Plan area = plan length × plan width. Slope factor = 1 ÷ cos(pitch angle). Sloped roof area = plan area × slope factor. Order area = sloped roof area × (1 + waste percent ÷ 100). Packs = ceiling(order area ÷ coverage per pack).

This is the method behind the answer, so the result can be checked rather than simply trusted.

Live math canvas

Your numbers, formula and explanation together

Roofing Calculator: 66.2 m². order area 72.82 m² · 25 packs

Formula applied

The exact method behind this answer

CalculationTime keeps the method visible so the number can be checked instead of blindly trusted.

Plan area = plan length × plan width. Slope factor = 1 ÷ cos(pitch angle). Sloped roof area = plan area × slope factor. Order area = sloped roof area × (1 + waste percent ÷ 100). Packs = ceiling(order area ÷ coverage per pack).

Apply the formulaPlan area = plan length × plan width. Slope factor = 1 ÷ cos(pitch angle). Sloped roof area = plan area × slope factor. Order area = sloped roof area × (1 + waste percent ÷ 100). Packs = ceiling(order area ÷ coverage per pack).66.2 m²order area 72.82 m² · 25 packs

Your live breakdown

Current inputs in the calculation

These values come from the controls above and update when the calculator changes.

Plan length: 10 m
Plan width: 6 m
Roof pitch: 25 degrees
Waste allowance: 10 %
Coverage per pack: 3 m²

Resulting answer

66.2 m²

order area 72.82 m² · 25 packs

Answer: 66.2 m²
Live support: order area 72.82 m² · 25 packs

Assumptions used

What this answer assumes

Material area only. Add ridge, valley, flashing, underlay, fixings and safety/access requirements separately.

The roof is treated as a simple rectangular roof plan with one pitch angle across the whole area.
Pitch is entered in degrees and converted with the cosine slope factor.
Coverage per pack is user-entered because shingles, tiles, metal sheets, membranes and rolls cover different areas.
The result is a material-planning estimate only. It does not replace site measurement, structural design, fixings, flashing, underlay, safety access or local building-code checks.

Master’s Tip

How to use the result well

Master’s Tip: measure hips, valleys, dormers, penetrations and starter/ridge pieces separately. A clean rectangle is useful for the first quote note, but real roofs often need extra line items before ordering.

Printable record

What belongs in the saved calculation

Save the inputs, result, formula, assumptions, page URL and date together so the calculation can be reviewed later.

Plan length: 10 m
Plan width: 6 m
Roof pitch: 25 degrees
Waste allowance: 10 %

What-if check

Waste and pitch sensitivity

Compare the same roof plan with different waste allowances and nearby pitch angles before turning the estimate into a supplier order.

Waste	Order area	Rounded packs
0.0%	66.20 m²	23 packs
5.0%	69.51 m²	24 packs
10.0%	72.82 m²	25 packs
15.0%	76.13 m²	26 packs

Pitch	Slope factor	Order area
20.0°	1.0642	70.24 m²
25.0°	1.1034	72.82 m²
30.0°	1.1547	76.21 m²

Visual proof

Plan area × slope factor

The sketch shows the core geometry: the flat roof plan is multiplied by a pitch slope factor, then waste and pack rounding are added separately.

Visual grid

This result measures part of the space you live in

Length, area, volume and material estimates are grid problems too: measure the space, account for edges and allowances, then turn the pattern into a number you can use.

Micro-timehours, minutes, shiftsHuman scaledays, weeks, projectsMacro-timemonths, years, calendars

Measured output66.2 m²

Space calculations turn a real surface, room, run or volume into cells, edges and allowances that can be quoted, ordered or checked.

66.2 m²order area 72.82 m² · 25 packs

Inputs

Plan length: 10 m
Plan width: 6 m
Roof pitch: 25 degrees
Waste allowance: 10 %
Coverage per pack: 3 m²

Method

Plan area is 10 × 6 = 60 m². At 25°, slope factor is 1 ÷ cos(25°) = 1.1034, so sloped roof area is 66.20 m². Add 10% waste to get 72.82 m². At 3 m² per pack, 72.82 ÷ 3 = 24.27, so round up to 25 packs.

Assumptions

The roof is treated as a simple rectangular roof plan with one pitch angle across the whole area.
Pitch is entered in degrees and converted with the cosine slope factor.
Coverage per pack is user-entered because shingles, tiles, metal sheets, membranes and rolls cover different areas.
The result is a material-planning estimate only. It does not replace site measurement, structural design, fixings, flashing, underlay, safety access or local building-code checks.

Notes

Use this space on the printed report for client, supplier, classroom, job-location, measurement, quote or approval notes.