TWR vs IRR: What's the Difference, and Which One Should You Actually Trust?
If you've ever looked at your brokerage's "return" number and felt like it didn't match reality, you're not imagining things. Most portfolio tools show you a single return percentage — and that number can be misleading in ways that actually matter to your decisions.
There are two different, correct answers to "what's my return?" — and they answer two different questions.
The problem with a single "return" number
Say you invested $10,000 on January 1st. The market did well, and by June your portfolio was worth $13,000 — a 30% gain. Excited, you added another $10,000 in June. By December, the market pulled back, and your portfolio ended the year at $21,000.
Is your annual return 5% (($21,000 − $20,000) / $20,000)? That's what a naive calculation gives you. But it's wrong — or more precisely, it's answering a question you didn't ask.
Time-Weighted Return (TWR): "How well did the investments themselves perform?"
TWR strips out the effect of when you added or withdrew money. It measures the performance of the underlying investments, independent of your personal cash flow timing.
This is the number professional fund managers report, because a fund manager doesn't control when investors deposit or withdraw money — TWR isolates their skill (or the market's performance) from your behavior.
Use TWR when: you want to compare your portfolio's performance against a benchmark (like the S&P 500) or against another investor, fairly — regardless of when either of you added money.
Internal Rate of Return (IRR): "How well did my money actually do?"
IRR (sometimes called XIRR when cash flows happen on irregular dates) is the annualized rate of return that accounts for the actual size and timing of every dollar you put in or took out. In the example above, IRR would correctly reflect that your second $10,000 didn't have as much time to grow as the first.
Use IRR when: you want to know the real, personal rate of return your capital earned — the number that matters when deciding "was this actually a good use of my money?"
A simple way to remember it
- TWR answers: "Did I pick good investments?"
- IRR answers: "Did I make good decisions about when to invest?"
They can — and often do — show meaningfully different numbers for the same portfolio. Neither is "more correct." They're correct answers to different questions, and a serious investor needs both.
Why most portfolio trackers only give you one (and usually the wrong one for the question you're asking)
Simple portfolio apps often show only a basic percentage gain, which is neither TWR nor IRR — it's a blended number that's misleading for both purposes. Calculating true TWR and IRR requires tracking every cash flow with its exact date, which is more engineering work than most spreadsheet templates or basic trackers bother with.
This is table-stakes analysis for a fund manager, and there's no reason a DIY investor should have less visibility into their own numbers than a professional does into a client's account.