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Roofing Calculator

Provide your roof measurements to this free roofing calculator and calculate the roof area and its construction cost.

House Width:

cm ▾

House Length:

cm ▾

Unit Price:

Roof Pitch:

m² ▾

Related

The roofing calculator lets you quickly calculate the area of your roof and estimate the cost to reconstruct it.

With this online tool, you can get a free roofing estimate in seconds.

Roof Area Formula

To estimate your roof area, use the formula:

Roof Area = Base Area / cos(Pitch (°))

How to Calculate Roof Size and Cost

Knowing the correct roof size is essential for accurate cost estimation. Roofs are measured in square footage, and contractors usually base their quotes on this area. An online roof calculator simplifies this process for both homeowners and professionals.

Step 1: Measure Roof Size

Measure the roof's length and width.
Calculate the base area: Base Area = Length × Width.
Determine the roof pitch:

Pitch (%) = Rise / 12 × 100%
Pitch (°) = arctan(Pitch (%))

Calculate the roof area using the pitch:
Roof Area = Base Area / cos(Pitch °)

Step 2: Estimate Roofing Cost

Determine the total roof area.
Find the unit price of your roofing material.
Multiply the roof area by the unit price to get the total estimated cost.

This helps you purchase the correct amount of asphalt shingles or other roofing materials efficiently. Using an online calculator saves time and avoids manual errors.

Practical Example

Suppose your house has:

Length (L) = 40 ft
Width (W) = 30 ft
Pitch = 5%

Solution:

Base Area = 40 × 30 = 1,200 ft²

Pitch in degrees = arctan(0.05) ≈ 2.86°

Roof Area = 1,200 / cos(2.86°) ≈ 1,201.5 ft²

If the unit price = $5 per ft², Total Cost = 1,201.5 × 5 ≈ $6,007.50

Using an online calculator can instantly provide both roof area and estimated cost without manual calculations.

Roof Pitch Table

Use multipliers to calculate roof area for different pitch angles:

Pitch	Angle	Multiplier
1/12	4.8°	1.003
2/12	9.5°	1.014
3/12	14.0°	1.031
4/12	18.4°	1.054
5/12	22.6°	1.083
6/12	26.6°	1.118
7/12	30.3°	1.158
8/12	33.7°	1.202
9/12	36.9°	1.250
10/12	39.8°	1.302
11/12	42.5°	1.357
12/12	45.0°	1.414

How Our Roofing Calculator Works

Quickly calculate roof area, material requirements, and total cost with just a few inputs.

Required Inputs

Roof Dimensions: Enter the length and width of your house
Roof Pitch: Provide the vertical rise relative to horizontal run
Unit Price: Cost per square unit of roofing material

Output You Will Get

Roof area in multiple units
Total roofing cost
Base area of the house
Roof pitch in degrees
Roof pitch ratio (x:12)

This tool helps contractors and homeowners estimate roofing costs accurately and get free estimates instantly.

FAQ

What is the most common roof pitch?

Standard roof pitches range from 10° to 25°. Steeper roofs are recommended in snowy or hilly regions for better drainage.

How many shingles do I need for a 1,200 sq. ft. roof?

Depends on shingle type and size, usually 1–2 per sq. ft. Use an online roofing calculator for precise estimates.

What are gable and shed roofs?

A Gable roof has two sloping sides meeting at a ridge; a Shed roof has a single sloped surface.

References

Iko.com: How to Estimate & Price a Roofing Job

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