It is based on the relative sizes of a man's nose, hands and feet.
The secret formula for assessing the size of a man's manhood has been developed by scientists, says condom maker Condomi.
The website delivers a man's vital statistics seconds after the relevant information is entered.
The "Condom Sizemograph" has been applied to celebrities, using photographs and information such as shoe sizes.
But Victoria Wells, Condomi's UK marketing manager, says it has a serious side.
"In addition to being good fun, the sizehimup.co.uk website is designed for more serious reasons," she said.
"Women account for 40% of condom buyers in the UK and we felt it was important that they had some assistance in choosing the correct product."
Disclaimer
Condomi has refused to give details of its formula in case it falls into the hands of competitors.
"It has been scientifically tested and shown to be accurate," said a spokeswoman.
However, the website has a disclaimer.
"The Condom Sizemograph is offered for entertainment purposes only," it says.
"Neither Condomi nor any of its subsidiaries or partners can be held liable for any losses incurred due to use of this service and its results.
"Most scientists assert there is no relationship between penis size and that of someone's feet, hands or nose."
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