How to calculate portfolio XIRR

What XIRR actually answers

XIRR finds an annualized rate that makes the present value of all cashflows consistent with today’s portfolio value — “what yearly return matches what I sent, withdrew, and still hold?”

ROI as “profit ÷ invested” ignores timing. TWR removes deposit effects to compare a strategy to an index. XIRR is a personal number about your money.

What data to prepare

For each move you need a date and signed amount: buys and fees as outflows (negative), sells and received dividends as inflows (positive).

At the end add today’s market value of open positions as a synthetic inflow (as if you sold everything). Without it XIRR does not “see” what you still hold.

Use one currency — typically CZK via CNB FX — or you mix apples and oranges.

Calculation steps

1) List all cashflows in order. 2) Add current value. 3) Compute XIRR (Excel/Sheets XIRR, or a tool like Investiv). 4) Be careful on very short horizons — annualization can produce extreme numbers.

Sanity check: flipping signs or omitting fees changes the result a lot — same for missing dividends.

Common mistakes

Counting only closed trades and ignoring open positions. Mixing CZK and EUR without conversion. Treating unrealized P&L as cashflow. Comparing XIRR directly to an index without TWR.