Car Insurance Groups Explained: What They Mean Before You Buy (UK)

When you look at a car for sale you’ll often see an insurance group — a number from 1 to 50. It’s a quick proxy for how expensive that car is to insure: group 1 is the cheapest, group 50 the most expensive. Because the group is baked into almost every quote, knowing it before you buy can save you far more than haggling over the asking price.

What is a car insurance group?

It’s a rating, set by Thatcham Research (with the Association of British Insurers), that every new car is assigned. Insurers use it as a starting point and then adjust for you — your age, postcode, mileage, no-claims bonus and history. So two people can pay very different premiums for the same group-10 car, but the group sets the baseline.

How insurance groups are decided

Thatcham looks at the things that make a car cheap or expensive to insure:

• Repair costs. How much parts cost and how long repairs take — measured in standardised crash tests. Cheap, easily-sourced parts mean a lower group.
• New and used value. A more expensive car costs more to replace after a total loss.
• Performance. Higher power and top speed raise the group — faster cars crash harder and more often.
• Security. Alarms, immobilisers and good anti-theft design push the group down.
• Safety. Better crash protection and assistance systems (autonomous braking, etc.) reduce injury claims and can lower the group.

This is why a small city car with a 1.0-litre engine sits near group 1, while the same shell with a turbocharged sport engine can be 15–20 groups higher.

How to check a car’s insurance group before you buy

• Check the exact version — make, model, engine size and trim. The model alone isn’t enough; a Ford Fiesta ranges from roughly group 2 to group 30 depending on engine and spec.
• Use a group checker (Thatcham’s tool, or the group lookup most comparison sites provide).
• Get a real quote. The group is a guide; an actual quote for your details is the only way to know what you’ll pay — so compare before you commit to a car.

A practical approach: shortlist two or three cars you like, check their groups, then run quotes for each before you decide. The difference between a group-8 and a group-22 version of “the same” car can be hundreds of pounds a year.