Blog Posts

A roofer measuring a tiled roof.

Calculating the Size of Your Roof

As much as we would like them to, roofs don’t last forever. You may not have owned your current home the last time the roof was replaced, so you might not even know what the process is or what it might cost you.

The first step to finding all of that out, is calculating the roof square footage. You can safely do this yourself, or your local Arizona roofing company can help. The area of your roof can tell you a lot about your upcoming project.

Roof Size Can Determine Which Materials You Use

Just by looking at your roof, or even knowing the square footage of your house, you can start to grasp how big or small the job might be.

Calculating the precise area of your roof, however, will give you a more accurate idea of how much roofing material you will need to buy. This number will also likely be a decision-making factor in other facets of the project.

For instance, it may influence whether you choose asphalt shingles or clay tiles. Some materials are cheaper than others, but some do better on houses with steep pitches.

Asphalt shingles are typically the cheapest material, but they only last about 15-30 years. This option might be a good fit for you if you believe you will be selling your home within that timeframe—or if you just need to utilize the most budget-friendly choice.

Asphalt shingles typically run about $5 per square foot. Some are high-quality, but they can also be cheap and flimsy, so it’s important to research the manufacturing brand and installation company to know if you’re getting a good product.

The longer the lifespan of your roof, the more expensive it’s going to be to replace. Clay tiles, for example, run about $10 per square foot, but can last over 100 years.


Part of calculating the size of your roof is measuring the pitch, or how steep it is. Some materials, like clay tiles, do best on steeper roofs. Concrete tile, specifically, can be a solid, slightly-less-expensive alternative to clay tiles.

Piles of roof tiles laid out on a roof. Text: Calculating the square footage of your roof will lead to how much roofing material you need to buy.

How to Calculate Square Footage of a Roof

In order to measure your roof, you really only need two things: a ladder and a measuring tape.

Option 1: Manually Measure Each Side

The easiest way to calculate square footage of a roof is to measure each plane, or flat portion. Measure the length and width, then multiply them together. Make sure you convert these measurements to feet (if measuring in inches, divide the measurement by 12).

Calculate the area of each plane on the house then add them together. That grand total is the square footage of your roof!

Option 2: Only Measure the Pitch

If you don’t feel safe on a ladder, or don’t have the equipment to make those large measurements, you have another option.

First you need the square footage of your house, or the footprint. Then you need to calculate the slope of the pitch. This number is found by taking the rise divided by the run:

  • Mark 12 inches horizontally from the edge of your roof. This is your run.

  • Measure straight up from the 12 inch mark. This number is your rise.

The slope is usually referred to as “rise in 12.” For example, if you measured your rise as 4 inches, your slope would be 4 in 12. From there, take that calculation (in this case 4/12), square it and add 1. This is your roof pitch multiplier.

This can definitely get a little complicated. However, once you calculate the slope, you can always use a chart to find the multiplier.

Multiply your house’s footprint by that multiplier, and you have the area of your roof.

There are plenty of online calculators that can help, too.

Roof pitch calculation graph. Text: To calculate the pitch of your roof, divide the rise by the run.

Turn the Square Footage into Squares

So you know the square footage of your roof. Does this mean you are ready to go to the hardware store and grab some shingles?

Well, yes and no. Most roofing materials aren’t measured in strictly square footage. They are measured in roof squares. The name might be confusing, but it’s a pretty simple conversion.

A roofing square refers to a 10 x 10 foot square on a roof. Once you measure your roof, divide that number by 100.

For example, you live in a small home and measure your roof as 1500 square feet. Your roof is actually 15 squares, and you should budget for materials based on that number. Most roofers recommend budgeting for an extra few squares due to waste during installation.

You Know the Size of Your Roof–What’s Next?

Knowing how to calculate roof area will help you estimate the costs of its replacement. However, many roofs are fairly complex with multiple sloping sides. To get the most accurate measurement, contact a trusted roofing company to take a look and give you an estimate.

Legacy Roofing has dedication and experience to make sure your re-roof project is high-quality and stays within budget. Give us a call today to get started on your new roof.

Schedule an appointment or inspection
with Legacy Roofing today!

If you would like Legacy Roofing to inspect your roof and offer a free estimate, please call us, or fill out the contract form below. Legacy will send a trained estimator to inspect and offer an experts opinion on the size and scope of your job.

Legacy Roofing LLC - Prescott
8360 E Pecos Drive
Prescott Valley, AZ 86314

phone icon928-460-4430

Repair Needed?