# Roofing Material Calculator

## Estimating Roof Materials

Calculate how much roofing material is needed for a roof size, as measured from the ground. Add the price per square of materials to get an estimate of material cost.

## How to Estimate the Size of a Roof

If you’re replacing a roof, the first consideration needs to be the size of the roof so accurate material estimates can be made. In the U.S., roofs are measure in square footage. Roofing contractors typically quote projects based on the size of the roof in squares. Consequently, gathering the roofs size in squares and square footage is the first step.

### Find the Area of the Footprint of the Roof

To calculate the size of the roof, you need to measure the size of the roof as if it were flat, account for roof pitch, calculate square footage, and finally determine how many squares of material are required for the roof. The calculator above can handle all of this, simply enter the length, width, and pitch and it will determine the size of the roof in squares.

Start by measuring the length and width of the roof in feet, as you’re standing on the ground. Remember that the length and width need to be found for the roof, not the house, so take into account that the roof overhangs the building. Then determine the area of the roof as if it were flat. This can be done by measuring the length in feet times the width in feet to get the area measurement. Remember that the area needs to be found in square footage, convert inches to feet, convert yards to feet, or convert meters to feet.

### Finding the Total Roof Area

Once the area of the roof’s footprint is known the overall roof area can be found by accounting for the pitch of the roof. The pitch of the roof is the rise over a 12 inch run. Use our roof pitch calculator to find the pitch of your roof. Next, multiply the footprint of the roof by the multiplier below for your roof pitch to find the overall roof area.

For example, a 4/12 pitch roof that is 100 square feet:

100 × 1.054 = 105.4ft^{2}

#### Roof Pitch Area Multipliers

Pitch | Multiplier | Pitch | Multiplier | |
---|---|---|---|---|

1/12 | 1.003 | 13/12 | 1.474 | |

2/12 | 1.014 | 14/12 | 1.537 | |

3/12 | 1.031 | 15/12 | 1.601 | |

4/12 | 1.054 | 16/12 | 1.667 | |

5/12 | 1.083 | 17/12 | 1.734 | |

6/12 | 1.118 | 18/12 | 1.803 | |

7/12 | 1.158 | 19/12 | 1.873 | |

8/12 | 1.202 | 20/12 | 1.944 | |

9/12 | 1.25 | 21/12 | 2.016 | |

10/12 | 1.302 | 22/12 | 2.088 | |

11/12 | 1.357 | 23/12 | 2.162 | |

12/12 | 1.414 | 24/12 | 2.236 |

### Finding the Size of the Roof in Squares

Roofing contractors estimate projects and materials by the square, so it is crucial to find this measurement to accurately estimate the amount of material needed. A square simply refers to a 10′ x 10′ square of roofing. This is simply 100 square feet of roof. To find the squares, divide the overall roof area by 100 and then round up. For instance, if the roof is 1550 square feet, then it is 16 squares.

## Estimating Roofing Materials

Although roofing projects are sold by the square, roofing material is often not.

The average bundle of shingles covers 33.3 ft^{2}, so 3 bundles of shingles are needed per square.

Roofing felt is sold by the roll. The average roll of 15 pound roofing felt covers about 400 ft^{2}, or 4 squares, while the average roll of 30 pound roofing felt covers about 200 ft^{2}, or 2 squares.

Nails will also be required for any roofing project. The average 3-tab shingle needs 4 nails per shingle. High wind areas and other types of shingles may need more. 320 nails will be needed to install a square of standard 3-tab shingles assuming 4 nails per shingle and 80 shingles per square.

Also, consider drip-edge that will be needed to protect the edge of the roof from rot, vents, and other materials such as flashing or caulk.

If you’re installing your own roof, be sure to understand everything that’s involved and be safe. The DIY Network has some great tips for doing your own roofing project. We recommend get free roofing estimates to understand the costs and any other project complexities.

In addition to accurately estimating materials, it is important to make sure you order extra material when ordering. Account for about 5-10% overage on your project to make sure you have enough material in the event that measurements are a little off or material is wasted or damaged. This is more critical for materials that are special order or have long lead times.

## Other Considerations

There are some other factors to consider when installing a new roof. Learn about the costs of installing a new roof. Many localities require permits and inspections for roofing projects, check with your local inspections office and consult local building codes for more information on the requirements. Also, consider that removing old materials may be a good idea and will require disposing of a large amount of waste. Plan ahead for this by ordering a dumpster for the project.

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