The question of when to pop the question has long vexed bachelors. Now, statisticians have devised a new formula that they claim will help men decide the right time to propose marriage to a potential bride.

An international team has come up with the formula which uses the 'theory of optimal stopping' – a sequential decision-making process used in finance and medical trials to pinpoint when to take an action to maximize expected rewards and minimize costs.

According to them, the probability formula suggests that men should propose marriage mostly as a joke, but it may actually work – in fact, it would give a 37 per cent chance of finding the best partner from a pool of marriage prospects.

"Probability isn't the most romantic basis for a marriage but while the formula won't fit everyone it does seem to fit a lot of couples, whether through accident or design.