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Decking Calculator

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Deck componentsDecking materialsCost to build a deck – how to use the deck material calculatorHow does the decking calculator work? – An exampleAdditional costsSourcesFAQs

The decking calculator can help you determine the number of decking boards and fasteners needed. It is also a tool for estimating the cost of building 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 to 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 find information about the deck's components, the different types of decking materials, and instructions on using the deck cost calculator.

We would also recommend working on the ambiance – planting 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.

  • Beam: the horizontal support structure for the deck frame, placed on the posts beneath the joists. Check out our wood beam span calculator to help you choose the right size of lumber for your beams.

  • Joist: the horizontal supporting boards beneath the decking. Our floor joist calculator can help you properly space your decking joists.

  • Decking (deck flooring): the surface of 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:


    • Pressure-treated softwood (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; and

    • Natural look.


    • 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); and

    • Fades in the sun.

  • Composite:


    • No splinters;

    • Unlikely to rot; and

    • Doesn't need a stain or other protective finish.


    • More expensive than wood;

    • Heavier than most woods;

    • Looks and feels artificial; and

    • Needs to be scrubbed to prevent mildew.

  • Plastic:


    • Light, easy to handle;

    • No rot; and

    • No maintenance (apart from cleaning).


    • More expensive than composite;

    • Looks and feels more artificial than composite; and

    • 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. Nevertheless, you can use our plywood calculator to help you with that. Just don't forget to apply some waterproofing sealant to protect your plywood decking.

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; or

  • Hidden fasteners – allow the creation of 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 of 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 that 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 a deck that is 20 ft long and 13 ft wide. To calculate the square footage of the deck, multiply the two numbers together:

    20 ft × 13 ft = 260 ft²

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

    6 in / 12 = 0.5 ft

  3. Let's calculate the square footage of one 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% to account for waste:

    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) needed, we follow the rule of thumb that you need 350 screws for every 100 square feet of decking. If we divide those values by 100, we can say that we need 3.5 screws for 1 square foot.

    That means that the number of screws is 3.5 times larger 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 screws, multiply the square footage of your deck by 7/2:

    7/2 × 260 = 910

    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 our 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 total cost of the boards, we need to multiply the price of one board by the total number of boards. If one board costs $7:

    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 the following:

  • 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 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 your deck. 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.


  • The 10 Essential Components of a Deck;

  • How To Choose The Right Material For Your Deck;

  • How to Plan Decking; and

  • How to Choose the Right Fastener for Your Deck.


What is composite decking?

Composite decking means that the decking boards are made by mixing recycled plastics, waste wood fiber, and bonding agents. Although wood is still the most common decking material, composites have the advantage that they can be more durable and require less maintenance.

What is the cheapest type of deck to build?

Pressure-treated wood is generally the cheapest material for decking. Its price can be as much as 20-30% lower than that of traditional wood. However, don't forget the long-term costs in the form of annual maintenance, such as staining or painting.

What size is a standard deck?

The average deck size is between 300 ft² and 400 ft². A deck measuring at least 12 feet by 12 feet should be enough for you to hold a round dining table. The size mainly depends on the amount of space you have.

In general, your deck should be wider than it is deep, and its longer dimension should run the length of the house.

How many deck boards do I need for a 12x12 deck?

You can calculate it in a few steps:

  1. Calculate the square footage of the deck: 12 ft × 12 ft = 144 ft².

  2. Choose the size of a single decking board, e.g., 8 ft long and 0.5 ft wide.

  3. Calculate the square footage of the decking board: 8 ft × 0.5 ft = 4 ft².

  4. Find the number of decking boards needed (plus 10% for waste): 144 ft² / 4 ft² × 1.1 = 40.

Size of your deck

Size of decking boards

Material estimations

Cost estimations

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