There are several ways to measure your ring size. If you already own a ring and would like to purchase another ring in that size, you can measure the internal diameter (inside the band, from one side to the other). Compare the measurement in mm to the diameter column in this chart to determine the UK ring size.
Alternatively you can use a thin strip of paper. Wrap it around the finger you want to wear the ring on and mark or tape in place. Make sure you can remove the paper ring so you know you will be able to get the ring on and off.
Measure from the start of the paper to where you made your mark in millimeters. Find the closest circumference measurement on the chart below. If it is between two sizes, choose the larger one.
Your finger size changes depending on weather and body temperature. For the best measurement, measure when your hands are warm.