Calculate the square footage of your deck instantly. Get your deck area, perimeter and an optional material planning allowance in seconds.
Designed for rectangular deck sections. Irregular decks can be calculated by dividing them into smaller sections.
Enter your deck dimensions below.
Optional allowance for cuts and material waste.
Deck Square Footage
0 sq ft
Deck Planning Tool
A deck square footage calculator helps you determine the total surface area of a deck using its dimensions. Square footage is useful for estimating decking materials, planning construction costs and understanding the overall size of your project.
For a simple rectangular deck, the calculation is straightforward: multiply the length by the width. For example, a 20-foot by 12-foot deck has a base area of 240 square feet.
Permitrust's free calculator also provides an optional material waste allowance so you can create a more practical purchasing estimate.
How It Works
Enter your dimensions and let the calculator handle the math.
Measure the length of your planned deck in feet.
Measure the deck width from one edge to the other.
Multiply length by width to determine square footage.
Add an optional allowance when estimating materials.
The Formula
For a rectangular deck, multiply the length by the width.
Basic Formula
Square Footage = Length × Width
Example: a 20-foot × 12-foot rectangular deck equals 240 square feet.
Examples
These examples show how common deck dimensions translate into square footage.
Material Planning
Your actual material order may need to be larger than the calculated deck area. Cuts, layout, damaged boards and installation can create material waste.
A simple rectangular design may require less cutting.
A practical planning allowance for material estimates.
More complex layouts can require additional material.
Designs with many cuts or angles may need more material.
Waste allowances are planning estimates, not universal requirements. Follow the decking manufacturer's recommendations and your project's actual layout.
Irregular Decks
If your deck is not a simple rectangle, divide the design into smaller rectangular sections. Calculate the square footage of each section and then add the results together.
Split the shape into rectangles that are easy to measure.
Calculate every section and add the square footage together.
Permit Planning
It can. Some jurisdictions consider deck size when determining permit requirements, fees or plan-review requirements. However, square footage is only one possible factor.
Total area may be relevant to local review requirements.
Setbacks, zoning and property location can affect requirements.
This calculator provides mathematical estimates for planning purposes. It does not replace professional measurements, construction drawings, manufacturer instructions or local building requirements.
Always verify final dimensions and material quantities before ordering materials or submitting a permit application.
Frequently Asked Questions
Square footage is only one part of planning a deck project. Check the permit, zoning, setback and construction requirements that may apply to your property.
Check My Permit Requirements