how to find rate of return

[racy]

I have been tracking the year end balance of a stock portfolio for many years. In some years the year-end balance is up, in some years it is lower. How would I find out the average rate of return of this series of results (thinking I could use this to predict the future,,, so I can retire early!)

Thanks.

[cycling-rod]

Put the year-end balance totals, whether up or down, for the number of years required (10 years, for instance) in a column, sum the column and then divide the summed total by the number of years. Use all the balances whether up or down.

Put in A11: =SUM(A1:A10)/10
Format A1 to A11 as Currency: £ or $