Seems to be no rhyme or reason to me! Certainly not clear enough for me to approximate cost per group. When I've tried comparison sites for potential purchases my annual mileage seems a far bigger factor than either group or value.

I realise much will depend on insurance company and other variables : however, I wondered if there is an approximate rule of thumb way to estimate increased costs if buying a car with higher group rating.

For example choosing between a car with a rating of 16 or one of 24 what would the rough cost of insurance variation be. Is there any consistency between premium and range of groups ?

Hope the question is reasonably clear !!! if not, apologies.

I use the What Car comparison - by comparing two cars from different groups (your existing and your proposed), calculate the % increase and then apply that % to your current premium. However, if there 's a big difference in age/value of the cars being considered then it is also affected by the value of each car.

Although HJ Car-by-car Reviews show the groups, I'm not aware of any typical insurance figure.

The insurance group rating system is managed by Thatcham on behalf of the Association of British Insurers, and is an advisory system. Being advisory, individual insurance companies may decide to use either a lower or higher insurance rating for certain vehicles depending on their experience, whether or not that vehicle is one they wish to insure, etc.