You may find this reckoner useful
This schedule shows the sizes of flowerpots in IMPERIAL dimensions as it has always done.We have been asked if we could convert these dimensions to METRIC and we have done so using a conversion rate of 25.4mm to the inch,
They are the best we can do and are as follows:-
3.5 inches - 89mm 6.5 inches - 165mm
4.5 inches - 11 4mm 7 inches - 178mm
4.75 inches - 121mm 8 inches - 203mm
5 inches - 127mm 9 inches - 229mm
6 inches - 152mm 10 inches - 254mm
16 inches - 400mm