How do I calculate the size of the tunnel with a banner or flag?

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With banners and flags it is possible to have a tunnel made in the fabric. We then make an open seam in your flag or banner, so that they can be slid over a pole. Unless otherwise stated, the open seam is measured 6 cm flat.

How do you calculate the size of this tunnel? There is a difference between a tunnel of 6 cm diameter and a tunnel of 6 cm measured flat. The 6 cm diameter does not fit in a 6 cm flat measured tunnel.

This is how it is calculated:

  • You know the diameter and you want to calculate the flat size: diameter x π / 2
  • You know the flat size and want to calculate the diameter: flat size / π

An example:

  • 6 cm diameter = 18.84 cm circumference = 9.42 cm flat.
  • 6 cm flat = 12 cm circumference = 3.82 cm diameter = 1.91 cm radius.