Calculate your deck's square footage, perimeter and overall dimensions in seconds. Use the results for project planning, material estimates and permit preparation.
Designed for simple rectangular deck layouts. Divide irregular decks into sections for a more accurate estimate.
Enter the planned deck dimensions.
Estimated Deck Area
0 sq ft
Deck Planning Tool
A deck size calculator helps you determine the total square footage and perimeter of a rectangular deck using its length and width. Knowing the size of your deck is useful when planning materials, estimating project costs and preparing information for a permit.
For a rectangular deck, the basic calculation is simple: multiply the deck length by the deck width to determine the deck area in square feet.
How It Works
Enter two measurements to get your deck's estimated square footage and perimeter.
Measure the longest dimension of the planned deck.
Measure the distance from the house or starting edge to the outside edge.
Multiply length by width to get square footage.
Use the result for materials, budgeting and permit planning.
Deck Size Formula
The square footage of a rectangular deck is calculated by multiplying its length by its width.
Formula
Deck Area = Length × Width
For example, a deck that is 20 feet long and 12 feet wide has an area of 240 square feet.
Project Planning
Knowing your deck dimensions gives you a better starting point for several parts of the project.
Square footage helps you estimate the amount of decking material required.
Larger decks generally require more materials and labor.
Some jurisdictions consider project size when reviewing permit requirements.
Accurate dimensions make drawings and project planning easier.
Irregular Decks
This calculator is designed for a simple rectangular deck. If your deck has an L-shape, multiple sections or another irregular layout, divide the design into smaller rectangles.
Break the deck into simple rectangular sections.
Calculate each section and add the square footage together.
Permit Planning
It can. Local building departments may consider the deck's size, height, location, structural design and connection to the home when determining permit and plan-review requirements.
Permit requirements differ between municipalities.
Height, setbacks, structure and location can also matter.
This calculator provides a mathematical estimate for a simple rectangular deck. It does not replace professional measurements, construction drawings or requirements from your local building department.
Always verify your final dimensions before ordering materials, preparing plans or submitting a permit application.
Frequently Asked Questions
Knowing your deck size is only the first step. Check the permit, zoning, setback and construction requirements that may apply to your property.
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