Roofing Calculator: Estimate Roof Area, Materials, and Cost

Welcome to our comprehensive guide on using a roofing calculator to estimate the area and materials required for your roof. This guide is tailored to help you navigate the process efficiently and accurately.

Roofing Calculator

Roofing Area Calculator



Estimated Roof Surface Area

roofing squares

bundles of shingles or rolls of roofing

rolls of #15 felt or rolls of #30 felt

rolls of self-adhered underlayment or rolls of ice and water shield self-adhered underlayment

Includes materials buffer 

Estimated Roofing Cost


This roofing calculator is provided for estimation purposes only and should not be considered professional advice. We are not liable for any inaccuracies or errors resulting from user input or application of the calculator's results. Users are responsible for verifying the output with a qualified professional and adhering to local codes and regulations.

Roof Pitch Rise Run Roofing Calculator

Understanding the Roofing Calculator Inputs

  1. House Base Area:
    • This is essentially the footprint of your house, the area it covers on the ground.
    • For rectangular houses, this is a straightforward length times width calculation.
    • For more complex shapes, you might need to break the area down into smaller segments or use an Area Calculator for an accurate figure.
  2. Roof Pitch:
    • This refers to the steepness of your roof, typically measured as a ratio of vertical rise over a horizontal run.
    • In the US, it’s usually calculated in inches per 12-inch run. For example, a 5/12 pitch means the roof rises 5 inches for every 12 inches of horizontal run.
    • The pitch is critical in determining the total roof area and affects the material requirements.
  3. Price (Optional):
    • You can input the estimated price per square foot for constructing the roof. This helps estimate the total cost required to cover your roof’s area.
Roof Pitch Angles

Estimating Roof Size and Materials

  1. Calculating the Base Area of the Roof:
    • Start by determining the area as if the roof was flat. Measure the length and width of the roof and multiply these dimensions.
    • Example: A roof length of 15 meters and a width of 12 meters gives a base area of 180 square meters.
  2. Adjusting for Roof Pitch:
    • The roof pitch affects the actual surface area of your roof. Use the appropriate multiplier from a Roof Pitch Table to adjust your base area calculation.
    • Example: For an 8/12 roof pitch, use the multiplier 1.202. Multiply this with the base area (180 square meters in our example) to get the adjusted roof area.
  3. Estimating Roofing Materials:
    • Based on U.S. standards, you’ll need different amounts of materials depending on your roof area.
    • For example, for every 33 square feet, you need a bundle of composition shingles. Rolls of roofing and felt have different coverage areas, so calculate the number of rolls based on your total roof area.

Practical Application

  • Example Calculation:
    • Let’s say your calculated roof area is 278.7 square meters (or 3,000 square feet).
    • For a buffer, you might require 33 roof squares (a roof square is a 10×10 foot area).
    • The estimated price could be around $14,998, considering a specific cost per square foot.
    • Material estimate would include 90 bundles of shingles, 30 rolls of roll roofing, and specific numbers of rolls for different felt types.
PitchAngleMultiply By
Roof Types

Different Roof Types

  1. Gable Roof:
    • Recognized by its triangular shape, this is one of the most common roof types.
    • It sheds water and snow efficiently and provides more space for the attic or vaulted ceilings.
  2. Hip Roof:
    • Characterized by slopes on all four sides that come together at the top to form a ridge.
    • Offers stability and durability, especially in high wind or snowy areas.
  3. Flat Roof:
    • As the name suggests, this roof appears flat with a very slight pitch for water drainage.
    • Commonly used in commercial buildings but also found in modern home designs.
  4. Mansard Roof:
    • A four-sided gambrel-style hip roof characterized by two slopes on each side.
    • The lower slope is steeper than the upper, often creating additional living space.
  5. Gambrel Roof:
    • Similar to a mansard roof but only has two sides.
    • Often seen in barns and farmhouses, offering maximum use of space under the roof.
  6. Butterfly Roof:
    • A V-shaped roof resembling a butterfly’s wings.
    • Allows for large windows, often used in modern architecture.
  7. Saltbox Roof:
    • Asymmetrical design with one side short and steep and the other long and sloping.
    • Originated in New England and offers a unique aesthetic appeal.
  8. Sawtooth Roof:
    • Features two or more parallel pitched roofs resembling saw blades.
    • Common in industrial buildings, now used in modern home design for aesthetic and functional purposes.

Roof Pitch in Detail

  • Definition:
    • Roof pitch is the angle of the roof’s slope, which is defined as the vertical rise over the horizontal run. It’s crucial for drainage, aesthetic, and practical purposes.
  • Measuring Roof Pitch:
    • Measured as the number of inches it rises vertically for every 12 inches it extends horizontally.
    • Common pitches include 4/12 (moderate) and 8/12 (steeper). A 4/12 pitch means the roof rises 4 inches for every 12 inches of horizontal run.
  • Importance of Roof Pitch:
    • Weather Resistance: Steeper pitches are better for rain and snow runoff.
    • Aesthetic and Design: Influences the overall look of the house. Steeper pitches can provide a more classic appearance.
    • Internal Space: Higher pitches can create more attic space or allow for vaulted ceilings.
    • Material Suitability: Certain roofing materials are better suited for specific pitches. For example, shingles work well on moderately steep roofs, while flat roofs may require specialized materials like tar and gravel.
  • Roof Pitch and Types:
    • Certain roof types have characteristic pitches. For example, mansard roofs have a steep lower slope, while most flat roofs have a very low pitch.

Hubert Miles | Licensed Home Inspector, CMI, CPI

Hubert Miles is a licensed home inspector (RBI# 2556) with more than two decades of experience in inspection and construction. Since 2008, he has been serving South Carolina through his company, Patriot Home Inspections LLC. As a Certified Master Inspector, Hubert is dedicated to providing his expertise in home inspections, repairs, maintenance, and DIY projects.