IF your Mr Right hasnt got round to proposing and seems more interested in his calculator, dont despair. He might just be working out his Optimal Proposal Age before popping the question. Boffins in Australia have come up with a quirky equation they say will predict the best age to get engaged with the promise of a long and happy marriage. For most people, it seems, thats 27. The 'Fiancee Formula works on the basis of how old a man is when he starts looking for a life partner - combined with the oldest hes prepared to be when he ties the knot. Using romance by numbers, he can calculate the optimum age to propose. 'Applying maths to matters of the heart is always a dangerous prospect, said Professor Tony Dooley from the University of New South Wales School of Mathematics and Statistics. 'But if you want to work out the right moment to start getting serious, then this actually gives you a mathematical framework to think about it. 'The result is your Optimal Proposal Age. 'Ideally you should not propose to anyone before you hit this age, but afterwards you should prepare to pop the question to the very next girl you date - as long as shes the best of the bunch so far The formula is based on a similar equation used in the finance and medical sectors to pinpoint when to take action to maximise rewards and minimise costs. And if you think a mathematical equation takes all the romance out of Valentine s Day, you may be right. The researchers claim a 37 per cent success rate, which doesnt sound very impressive. But they say traditional ways of picking a bride dont guarantee a successful marriage, either. 'Although probability isnt the most romantic basis for a marriage, the formula does seem to fit a lot of couples, whether through accident or design, Prof Dooley said. 'One could argue that the current, less structured approach to picking a marriage partner hasnt been 100 per cent successful, so perhaps its time for men to consider following a stricter set of rules when it comes to marriage planning. First the mathematicians worked out a fiendishly complex equation: ? (n-k) (n-k-1) (n-k-2) ... (n-k-r+2) x k x (1) n (n-1) (n-2) (n-r+2) (n-r+1) (r-1) The answer they came up with was 0.368 and thankfully that can be fed into a much simpler ready reckoner - set out in our step-by-step guide - that men can use to work out the right age for them. So, ladies, get your boyfriend number crunching, and hope he comes up with the right answer on February 14th. Maybe, as the researchers say, 'Any advice is good advice when it comes to courtship calculations. Daily Mail