Square to Linear Conversion

The calculation required to convert square metres to linear metres can, on first impressions, seem rather complicated.

It helps to think in terms of the number of linear metres required to cover an area of 1 square metre, (1m x 1m).

To calculate this, first assume that the 1m ‘length’ of the area is always covered by 1m long decking boards.

Then, establish how many boards need to be laid side by side to cover the areas 1m ‘width’.

As we allow 5mm for spacing alongside each board, we assume a 140mm wide decking board provides 145mm width of face coverage.

(Please note, not all decking boards are fitted with 5mm spacing, but this is a fair average to adopt for the purposes of a standard calculation).

Given that the total width of the area to be covered is 1m (or 1000mm), a total of 6.9 boards are required, (1000mm ÷ 145mm).

If these boards are laid to end, they would provide a total linear metre run of 6.9 – the amount required to cover a one square metre area.

This ratio can be used to calculate the linear metre equivalent of any m2 area being covered by a 140mm wide board and vice versa.

For instance:
50 square metres x 6.897 = 344.85 linear metres
100 linear metres ÷ 6.897 = 14.5 square metres


A simple formula can be used to establish the conversion ratio for any width of decking board:

Conversion ratio = 1000 ÷ (width of board in mm + 5mm)

Some common examples, rounded to two decimal places:

90mm Board = 1000 ÷ 95 = 10.53
115mm Board = 1000 ÷ 120 = 8.33
130mm Board = 1000 ÷ 135 = 7.41
140mm Board = 1000 ÷ 145 = 6.90
145mm Board = 1000 ÷ 150 = 6.67

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