I have switched frequently between ISA providers and I want to see how much my investments have truly increased.

I have a spreadsheet where column 1 is the date I invested a certain amount, column 2 is the amount invested on that day, column 3 is the value of that investment today, column 4 is the absolute percentage increase, and column 5 is the annualised percentage increase.

Note that the amounts are irregular. The dates are also irregular. The percentage increases are also irregular, as there are different funds / fees.

I want to calculate a time weighted return, but all of the formulas I've found online seem to want to know the full value of your portfolio at several points. How can I calculate a time weighted return witth the data I have? Thanks

  • 1
    I don't think it's possible without number of shares per investment, or value each time you moved money in or out.
    – keshlam
    Commented Feb 10 at 19:29
  • "I have switched frequently between ISA providers" As an investor? " I want to see how much my investments have truly increased." What prompted you to want TWR as a metric? I wonder whether this is an XY problem. There are methods of finding an estimate/proxy for the TWR, but given that any metric would be using other metrics to get a proxy, maybe you should just use those metrics? Commented Feb 13 at 3:42

1 Answer 1


For time-weighted return, you need the value at the time of each cashflow (purchase/sale). You can start with the value either before or after the cashflow, since you can add or subtract the cashflow to get the other amount.

Time Weighted Return is then just the product of each periodic return, taking the amount after the cashflow that started the period and the value before the cashflow that ended it.

So having the current value of each purchase is not enough, you need the value of the portfolio at the time of each purchase.

The fact that the amounts and timeframes are irregular is not important - TWR does not depend on either being regular.

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