How many cement bags are needed per m³ of concrete?

For standard concrete (250 kg/m³ mix), you need 5 bags of 50 kg per m³. For structural concrete (300 kg/m³), use 6 bags. This calculator uses the typical dosage for each element type.

Why should I add a wastage percentage?

On-site losses from spillage, unusable mixes and level corrections always occur. Adding 5–10 % to your final order ensures you don't run short of material.

What is the difference between mass concrete and reinforced concrete?

Mass concrete has no steel reinforcement and is used for low-load foundations. Reinforced concrete includes steel bars that provide tensile strength, making it suitable for slabs, columns and beams.

Quartile Calculator

Last updated: 2026-05-07

Use the Quartile Calculator to get instant, accurate results. Enter your values below.

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Enter values and press Calculate

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Common Sizes — Click to Fill

roof_length (m)	roof_width (m)	roof_pitch	shingles_per_bundle (pcs)
8 m	5 m	4	33 pcs
10 m	7 m	4	33 pcs
12 m	8 m	6	33 pcs
15 m	10 m	6	33 pcs
20 m	12 m	8	33 pcs

What is the Roofing Shingle Calculator?

Ordering the wrong amount of roofing shingles is an expensive mistake — shingles are sold in bundles and squares, and prices vary widely. Too few and the job stops mid-roof; too many and you're paying for materials you'll never use. The Roofing Shingle Calculator accounts for your roof's actual pitch using the pitch factor formula, so you get an accurate bundle count for sloped roofs of any angle.

You may also find the Drywall Calculator, Insulation Batt Calculator, and Concrete Steps Calculator useful.

Who Uses This Calculator?

This tool is used by homeowners re-roofing a house, roofers estimating material costs, and contractors preparing bids.

How to Use the Roofing Shingle Calculator

Enter your Roof length.
Enter your Roof width.
Enter your Roof pitch.
Enter your Shingles per bundle.
Click Calculate to see your results instantly.

Formula

The calculator uses the following formula:

Pitch factor = sqrt(1 + (pitch/12)²); Roof area = L × W × pitch_factor; Bundles = ceil(area ÷ 9.29 × 3)

Worked Example

A roof that is 12 m long × 8 m wide with a 6/12 pitch has a pitch factor of 1.118, giving an actual area of 107 m². That requires approximately 35 bundles (3 bundles per square, where 1 square = 9.29 m²).

Step-by-Step Calculation

Flat footprint: 12 m × 8 m = 96 m²
Pitch factor for 4/12 pitch: sqrt(1 + (4/12)²) = 1.054
Actual roof area: 96 × 1.054 = 101.2 m²
Roofing squares (1 square = 9.29 m²): 101.2 ÷ 9.29 = 10.9 squares
Bundles (3 per square + 10% waste): ceil(10.9 × 3 × 1.1) = 36 bundles

Common Mistakes to Avoid

Using the floor footprint area instead of actual roof surface area
Forgetting to account for roof pitch when ordering materials
Not adding 10-15% for waste, valleys, and hip cuts

Pro Tip: Always order 10–15% extra for waste, ridge caps, hips, and valleys. Shingles from the same production run have matching colour — mixing runs can cause visible colour differences.

Frequently Asked Questions

What is a roofing square?

A roofing square equals 100 square feet (about 9.29 m²). Most shingles come 3 bundles per square, though premium architectural shingles may need 4 bundles per square.

How does roof pitch affect material quantities?

Steeper roofs have more actual surface area than their footprint suggests. A 12/12 pitch (45°) requires 41% more shingles than a flat area of the same floor dimensions.

What is the pitch factor and how is it calculated?

Pitch factor = √(1 + (pitch/12)²). For a 6/12 pitch: √(1 + 0.25) = 1.118. Multiply your floor area by this factor to get actual roof surface area.

Do I need to include the overhang in my measurements?

Yes — measure the full roof surface including any eave overhang, not just the building footprint. Overhangs typically add 15–30 cm per side.

How long do asphalt shingles last?

Standard 3-tab shingles last 20–25 years. Architectural (dimensional) shingles last 30–50 years. Metal roofing can exceed 50 years. Lifespan depends on climate, ventilation, and installation quality.

Written and reviewed by the CalcToWork editorial team. Last updated: 2026-05-07.