Please excuse the title of this article from my friend, Professor Maria Nedeva. 

Actually, the name F*ck That Index (or FTI) came from a contributor answering a question on Quora, rather than Maria herself.

But it does adequately describe the purpose of this calculation, which is designed to help you understand, at a glance, whether or not you can afford to retire.

It's a fairly simple calculation; your age multiplied by your net worth divided by your annual spending.

Come up with an index reading over 1,000, and (according to this suggestion) you're in a strong enough financial position to retire.

In this article, Maria admits that her own FTI is 1,705. This means that, technically speaking, she can afford to retire today and faces a very low risk of running out of money before the end of her life.

I'm not a big fan of financial rules of thumb; they are often too crude and generic to fully reflect the intricacies of real-life financial planning.

But as a place to start thinking about the affordability of giving up work to retire, the F*ck That Index is a pretty good place to start.