You need to enter the age range of each partner you've had and the calculator works out how many previous sexual partners people in that age range have had. It then repeats the process for five further 'generations' of partner to give you your (scary!) total. Have a go here!
It's a bit of fun, but the underlying issues are serious. The tool was developed to raise awareness of sexually transmitted diseases. Clare Kerr at Lloydspharmacy says: 'It's important that people understand how exposed they are to STIs and take appropriate precautions including using condoms and getting themselves checked out. The majority of STIs are easy to rectify, but if left untreated, the long term implications can be very serious.'
Where to next?
Tips for help with STIs
Sexual health advice - your questions answered