To help you find your ring size, you can use the below charts. If you have access to a printer, just print out the below page, take off your existing ring, and draw around the inside, you should probably do this 3 times to avoid any random results. Measure the inside width of the circle you’ve drawn, and then compare this to the above chart. You can also place your existing ring over the circles, to find the closest fit.

If you don't currently have a ring, the best method is to use a strip of paper (Not string, as string stretches!) mark the crossover point of the paper , take a measurement and compare to the chart, this method is slightly less accurate, but will at least give an approximation

Ring Size(UK)	Measurement(mm)	Ring Size(UK)	Measurement(mm)
A	37.8	N	53.8
B	39.1	0	55.1
C	40.4	0	55.1
D	41.7	0	55.1
E	42.9	0	55.1
F	44.2	0	55.1
G	45.5	0	55.1
H	46.8	0	55.1
I	48.0	0	55.1
J	48.7	0	55.1
K	50.0	0	55.1
L	51.2	0	55.1
M	52.5	0	55.1