David Beckham has no idea of the value of ''brand Beckham''.

The 42-year-old retired soccer star - who has children Brooklyn, 18, Romeo, 15, Cruz, 12, and six-year-old Harper with wife Victoria - has enjoyed a number of lucrative endorsement deals with a host of companies, including Adidas, Coty, H&M, Sainsbury's, and Samsung, and while he doesn't have ''a clue'' about his worth, he is ''proud'' of the way he's grown his empire.

He told CNBC: ''I wouldn't have a clue. But what I am proud of is that we've made it into a successful business, and that obviously coming from being a sportsman and then ready to jump into the business side of things, that it's all about having the right people around you, the right friends, family (and the) right business partners.

''And that has helped me transition from being a football player to a businessman and that's something that I'm excited about and very proud of. To put a price on it, I don't think I could. I'll leave that to someone else to decide.''

However, an industry expert has estimated David will earn up to £100 million a year from business deals

Richard Thompson, chair of talent agency M&C Saatchi Merlin, told CNBC's 'Marketing Media Money': ''You would look at David Beckham. I think you should be earning £100 million a year in your wealth, in a sense of royalty streams, equity value and fees (of) £50 to £100 million a year.

''But you know (that) should be where he's at. And if he's not, then he should be.''