Decking Calculator

Created by Rita Rain
Reviewed by Bogna Szyk and Jack Bowater
Last updated: Jun 17, 2022

The decking calculator can help you determine the number of decking boards and fasteners needed. It is also a tool for estimating the cost to build a deck (mainly focusing on deck flooring).

Imagine yourself sitting on a wooden porch on a warm, sunny, Sunday morning; sipping tea, reading a book, and taking in those sweet summer smells. You have the space take many of your activities outside, and can even throw a terrace party for your family and friends. A deck can be a great extension to your house and can bring more hygge into your life, but we'll stop with the romanticism - how much does it cost to build a deck?

The decking calculator can help you answer this question. In the following article, you will also find information about the deck's components, the different types of decking materials, and instruction on how to use the deck cost calculator.

We would also recommend working on the ambience - plant in some flowers next to your deck, or maybe building a pool to cool down in during hot summer days.

Deck components

To give you some idea about how a deck is constructed, let's take a look at the parts that make up a deck:

  • Posts: vertical framing support for beams and joists.

  • Beams: the horizontal support structure for the deck frame, placed on the posts, beneath the joists.

  • Joist: the horizontal supporting boards beneath the decking.

  • Decking (deck flooring): the surface - the layer of decks on the joists.

  • Fasteners: nails, screws, or hidden clips to attach decking boards.

Here we will focus only on the decking materials, but if you want to know the total cost to build a deck, you'll need to take into account the price of the substructure (posts, beams, and joists).

Decking materials

To estimate how much it will cost to build a deck, you need to decide on the types of materials you are going to use.

1. Decking boards:

Deck flooring can be made of natural wood, synthetics, or composite (a mixture of plastic and wood). Different types vary in looks, price, availability, need for maintenance, and resistance to rot, decay and insects.

Here is a rough comparison of the materials:

  • Wood:

    Pros:

    • pressure-treated soft wood (pine, fir, hemlock) is the cheapest option
    • redwood and cedar are lightweight, and at the same time prone to rot and insects
    • exotic hardwoods are durable
    • best when you want to make the decking yourself
    • widely available
    • natural look

    Cons:

    • redwood and cedar are soft and easily damaged
    • exotic hardwoods (teak, ipe) are more expensive than composite, and are heavy and hard, which can make them unwieldy
    • needs maintenance (power-washing, restaining)
    • less durable (prone to decay and rot)
    • fades in the sun
  • Composite:

    Pros:

    • no splinters
    • unlikely to rot
    • doesn't need a stain or other protective finish

    Cons:

    • more expensive than wood
    • heavier than most woods
    • looks and feels artificial
    • needs to be scrubbed to prevent mildew
  • Plastic:

    Pros:

    • light, easy to handle
    • no rot
    • no maintenance (apart from cleaning)

    Cons:

    • more expensive than composite
    • looks and feels more artificial than composite
    • needs special fasteners

Alternatively, you can go for plywood decking - it is cheap, fast and easy to install, but you may have a problem with standing water, which can damage the deck.

2. Fasteners:

You'll need to choose one of those:

  • Screws - easier to remove than nails

  • Nails - driving them is a bit faster, but if you do this incorrectly you may mar the wood, and removing a nail is more difficult than removing a screw

  • Hidden fasteners - allow the creation a smooth surface, but you'll need deck boards with a grooved edge of a size that is compatible with the clips

Cost to build a deck - how to use the deck material calculator

  1. Determine the length and width of your deck - you can do this by marking out the corners your designated building area with stakes, putting a string between them, and measuring the length of the line with a measuring tape.

  2. Enter the values into the decking calculator. It will output the square footage of your deck.

  3. Enter the length, width, and price of the decking boards you've chosen. The calculator will tell you the square footage of the boards.

  4. Choose the type of fasteners you will use, and the deck cost calculator will output the number of fasteners needed.

  5. Take a look at the number of screws, nails, or hidden clips needed. Find a pack which contains an equal or larger number and enter its price into the deck material calculator. The calculator will estimate the cost of building your deck.

How does the decking calculator work? - An example

If you want to know what equations the deck cost calculator uses, or want to calculate the cost yourself, read the example below.

  1. Let's say you want the deck to be 20 ft long and 13 ft wide. To calculate the square footage of the deck, multiply the numbers:

    20 ft * 13 ft = 260 ft²

  2. You chose a board which is 8 ft long and 6 in wide. Convert the width to feet - simply divide the value by 12:

    6 in / 12 = 0.5 ft

  3. Let's calculate the square footage of the decking board:

    8 ft * 0.5 ft = 4 ft²

  4. Now we can calculate the number of decking boards needed. We divide the deck square footage by the board square footage and add 10% of wastage:

    260 ft²/ 4 ft² * 1.1 = 71.5

    Let's round the result up (it's better to have more than less) - we'll need 72 boards.

  5. For calculating the number of screws (or nails), we use a rule of a thumb - 350 screws for every 100 square feet of decking. If we divide those values by 100, we can say that we need 3.5 screw for 1 square foot.

    That means that the number of screws is 3.5 times bigger than the number of square feet of decking. The equation would be:

    s = 3.5 * d or s = 7/2 * d

    To know the number of the screws, multiply the square footage of your deck by 7/2:

    7/2 * 260 = 910

    Then choose a pack with the number of screws closest to the value we calculated (remember you need to have more, rather than less).

    The closest number the distributor offers in a pack is 1000, and its price is 98$.

  6. If you go for hidden fasteners, you'll need half the number of the screws:

    7/4 * 260 = 455

    In this case, the hidden fasteners we need are available in a pack of 500.

  7. To know the cost of boards, we need multiply the price of one - let's say 7$ by the number of boards:

    72 * 7$ = 504$

    The boards will cost 504$.

  8. To know the cost of decking, let's add the price of the pack of screws to the price of boards:

    504$ + 98$ = 602$

    The total cost of deck flooring is 602$.

Additional costs

Some costs are not included in the deck material calculator. You may need:

  • Substructure - the price depends on the type of wood you choose and the size of your deck.
  • Permit - building a deck may require a license from your city.
  • Stairs and railings or balusters - you'll need those if you want a raised deck. Learn how many balusters and spindles you would need and how much to space them between each other using our spindle spacing calculator.
  • Paint - if you'd like to change the color of the decks. You can determine how much stain you need for your deck with some simple area calculations.
  • Labor - the cost of hiring a professional, if you don't want to build a deck yourself.

Sources

https://www.angieslist.com/articles/4-deck-parts-you-need-know.htm

https://www.popularmechanics.com/home/how-to-plans/how-to/a3490/4275113/

https://www.diy.com/ideas-advice/how-to-plan-decking/CC_npci_100129.art

https://www.bhg.com/home-improvement/deck/building/how-to-choose-deck-fasteners/

Rita Rain
Size of your deck
Length
ft
Width
ft
Square footage
ft²
Size of decking boards
Length
ft
Width
in
Square footage
ft²
Material estimations
Number of boards
Fasteners used
screws/nails
Number of screws/nails
Cost estimations
Price per board
$
Price for all boards
$
Cost of fasteners
$
Total cost
$
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