How to calculate decking board quantities

Calculate decking board quantities
Calculating decking board quantities is relatively straight forward.

1- Calculate the amount of decking board rows

To calculate decking board quantities required to build a deck is relatively simply process. It is best to start by working out how many rows of decking boards are needed. To do this, measure the width of the deck ensuring you allow for the fascia board and the decking overhang (a detailed outline can be found in the “Installing decking boards” guide). Then divide the width of the deck by the width of your decking boards plus the gap between the decking boards, which is recommended to be 3-4mm. Your calculation should look like this:

“Overall width of the deck in millimetres” / “decking board width in millimetres + spacing between decking boards in millimetres” = the number of rows of decking boards required. (It is always best to round up the answer to the next whole number.)

Example: If the deck is 3 metres wide and 5 metres long (including fascia board and decking board overhang) and the decking boards are 90mm wide and using a 4mm spacing between decking boards, your calculation would be:

3000/(90+4) = 3000/94 = 31.9149 which you would round up to 32.

This deck will require 32 rows of decking boards.

2- Calculate the total decking board lineal meters

Next, we need to work out the total lineal metres of decking required.

Multiply the “number of rows” by the length of the deck – again ensuring to allow for the fascia and the overhangs on both sides of the deck. I suggest and recommend allowing 10% for waste. The final calculation is as follows:

“Number of decking board rows” x “length of the deck in metres” x “1.1″ (multiplying by 1.1 automatically adds on the 10% waste) = total lineal metres.

Using the previous example your calculation would be:

32 x 5 x 1.1 = 176 lineal metres.

Now we have the figure for the total lineal metres of decking boards we need to order.

For more detailed information on how to calculate decking board quantities and how to install your decking boards correctly; you can purchase your own copy of our “Installing decking boards” guide or you may like to visit the “Resource Shop

7 Replies to “How to calculate decking board quantities”

    1. Hi Richard, Do you have any more details for your deck? For example, is your deck close to the ground or more than 1m off the ground which would need a handrail.

  1. We arelooking at diagional running decking house wall corner 4m x 7.5m x 8.5 a do we order timber lengths without waste…prob merbu

  2. I have an area I am thinking of getting a deck installed it is 9 meters by 5 meters the boards will run the long way 9meters , I need a price of what it would cost in materials for both size merbu 90mm and 140 and how much material I will require it is going partial over a concrete slab and some grass so stumps will need installing maybe around 8-12 ?

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