The BBFC

The bbfc have set out classification guidelines to help show people which films are suitable for certain age groups.

U - It is impossible to predict what might upset any particular child. But a ‘U’ film should be suitable for audiences aged four years and over. ‘U’ films should be set within a positive moral framework and should offer reassuring counterbalances to any violence, threat or horror. If a work is particularly suitable for a pre-school child to view alone, this will be indicated in the Consumer Advice.

PG - General viewing, but some scenes may be unsuitable for young children Unaccompanied children of any age may watch. A ‘PG’ film should not disturb a child aged around eight or older. However, parents are advised to consider whether the content may upset younger or more sensitive children.

12A/12 – Suitable for 12 years and over Exactly the same criteria are used to classify works at ‘12A’ and ‘12’. These categories are awarded where the material is suitable, in general, only for those aged 12 and over. Works classified at these categories may upset children under 12 or contain material which many parents will find unsuitable for them. The ‘12A’ category exists only for cinema films. No one younger than 12 may see a ‘12A’ film in a cinema unless accompanied by an adult, and films classified ‘12A’ are not recommended for a child below 12. An adult may take a younger child if, in their judgement, the film is suitable for that particular child. In such circumstances, responsibility for allowing a child under 12 to view lies with the accompanying adult. The ‘12’ category exists only for video works. No one younger than 12 may rent or buy a ‘12’ rated video work.
15 – Suitable only for 15 years and over No one younger than 15 may see a ‘15’ film in a cinema. No one younger than 15 may rent or buy a ‘15’ rated video work.
18 - Suitable only for adults No-one younger than 18 may see an ‘18’ film in a cinema. No-one younger than 18 may rent or buy an ‘18’ rated video.

R18 - To be shown only in specially licensed cinemas, or supplied only in licensed sex shops, and to adults of not less than 18 years The ‘R18’ category is a special and legally restricted classification primarily for explicit works of consenting sex or strong fetish material involving adults. Films may only be shown to adults in specially licensed cinemas, and video works may be supplied to adults only in licensed sex shops. ‘R18’ video works may not be supplied by mail order.

http://www.bbfc.co.uk/downloads/pub/Guidelines/BBFC%20Classification%20Guidelines%202009.pdf