I like calculating my personal portfolio's returns and have been using the true time weighted method, multiplying returns between successive cash flow events. One thing I've found is that because I hold both CAD and USD in my accounts is that I have to convert everything to CAD to calculate the returns. This presents a problem because the forex rate fluctuations affect the return. For example, for 2015, I had a 9% return is my RRSP, but the markets did horribly-my return only looks good because most of my assets are in USD which when converted to CAD looks pretty good. Is it better to have two different return rates, one for USD and one for CAD? I've also used the Modified Dietz method but apparently the true time weighted is the most accurate. What is the most accurate reflection of the true returns of a portfolio taking into account holding multiple currencies?