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Roofing Calculator

Table of contents

How do I calculate the roof area?Estimating the cost of the roofFAQs

The roofing calculator allows you to determine the area of the gable or shed roof of your house and to accurately estimate its cost. All you have to know are the dimensions of your house and the roof pitch, and this roof cost calculator will do the rest for you. Let's get started!

How do I calculate the roof area?

To calculate the area of your roof:

  1. Begin with calculating the area of your house in a plane parallel to the ground.

  2. Determine the roof pitch of your house.

  3. Once you know these values, you will be able to calculate the roof area. Begin by converting the roof pitch to an angle expressed in degrees using the following formulas:

    pitch(%) = x / 12 × 100%

    pitch(deg) = arctan[pitch(%)]

  4. Then, use the following equation to find the total area of the roof:

    roof area = base area / cos[pitch(deg)]

🙋 Roof pitch is the slope created by the rafters. If you don't know how to calculate it, head to our roof pitch calculator. You can input it either in degrees, as a percentage, or as a ratio of x:12.

Estimating the cost of the roof

Once you know the area of the roof, you have to decide on the scope of work. Do you want to build the roof from scratch or maybe replace the old layers? You also need to decide on the finishing material. For example, asphalt shingles will be less expensive than clay tiles.

After you've made all of these decisions, it's best to contact your local contractor and ask about the cost of both materials and labor per square meter or square foot of roof area. Remember that this unit price should include all additional elements such as fasteners, as well as the cost of removing all layers and disposing of them (if applicable).

The most typical cost of roofing falls between $2 and $4 per square foot (including labor). If the price proposed by your contractor deviates from these values, it is advisable to check with other contractors before starting the work.

If you cannot contact any contractor, calculate the cost of materials (for example, by going to the nearest construction store) and multiply this price by 2.5. You will obtain an approximate price including labor, assuming that 40% of the cost is taken by the materials and 60% by the labor.

The last thing you have to do is to multiply this cost by your roof area and voilà, you now know the total cost of your roof! Remember that the real cost might differ from this value a bit due to waste, so plan ahead and assign more funds to this construction work.

If you are not on a tight budget, maybe you'd like to add solar panels. If so, we have a solar panel calculator to help you.☀️

Also, make sure to take a look at our concrete slab cost calculator, too!

💡 If you are building a roof, our rafter length calculator may be just what you need. Or if you get a lot of snow where you live and ensure your roof can cope, check out our snow load calculator.


What are gable and shed roofs?

The definitions of a gable and shed roof are as follows:

  • A gable roof means there are two sloping sides that meet at a ridge.
  • A shed roof means there is only one flat surface, and it slopes to one side.

What is the most common roof pitch?

The standard roof pitch is between 10 and 25 degrees. Choose a higher value (steeper roof) if you live in an area where it snows a lot: the snow will slide off the roof more easily.

What is the roof area of a 100 sq m house with roof pitch of 25 deg?

The roof area is 110.34 sq m. To arrive at this result, divide the house area by the cosine of the roof pitch: 100 / cos(25 deg) = 110.34.

How do I estimate the cost of roofing?

To estimate how much you'll have to pay for a new roof, follow these steps:

  1. Determine the area of the roof.
  2. Find out the unit price of roofing (per square meter or square foot of roof area, depending on what unit you used in Step 1). Verify if it includes labor!
  3. Multiply the area of the roof by the unit price.
  4. The result you've got is the estimated cost of roofing.

House dimensions

Roof pitch

Enter any single value to calculate the others.

Roof cost

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