How to measure existing sign post diameter

When replacing or refitting signs, it’s important to correctly measure the diameter of the existing post to ensure you select the right size clips, caps, and finials. An accurate measurement will save time, prevent returns, and guarantee a secure fit.

Tools You’ll Need

• A tape measure or flexible measuring tape

• A piece of string (useful for large or awkward posts)

• A caliper (digital or manual) – for the most precise measurement

Step-by-Step Guide

1. Use a Tape Measure or Flexible Tape (Simple Method)

1. Place the tape measure across the top of the post, making sure it spans the widest point.

2. Read the measurement from edge to edge – this gives the outside diameter.

3. Keep the tape straight and level to avoid errors.

2. Use String or Flexible Tape Around the Post (Circumference Method)

1. Wrap the string or flexible tape tightly once around the post.

2. Mark where it meets and measure the length with a ruler.

3. Divide this measurement by π (3.142) to calculate the diameter.

3. Measure with a Caliper (Most Accurate Method)

1. Place the caliper jaws around the outside of the post.

2. Record the reading in millimetres.

3. Compare the result to standard post sizes (commonly 50mm, 60mm, 76mm, or 89mm).

Tips for Accuracy

• Always measure the outside diameter, not the inside.

• Take measurements in millimetres for best compatibility with fittings.

• Double-check by measuring in two directions to confirm roundness (older posts can become slightly oval).

• Match your result to the nearest standard post size before ordering.

Example Reference Table

✅ Once you know your post’s diameter, you can confidently order the correct sign post clips, caps, and finials for a secure and professional fit.