Investing · 6 min read

Understanding XIRR vs. CAGR for Irregular Investments

CAGR needs one clean start and end date — XIRR is the version built for the messier reality of a SIP, a top-up, and a partial withdrawal all happening on different days.

Why CAGR breaks down for irregular cash flows

CAGR assumes a single investment made on one date and withdrawn on another — it has no way to account for multiple contributions of different sizes made on different dates, which describes almost every real SIP, top-up, or partial-withdrawal history. Applying a CAGR-style calculation to that kind of cash flow produces a misleading number.

What XIRR does differently

XIRR (Extended Internal Rate of Return) finds the single annualized rate that, applied to every individual cash flow on its actual date, would explain the final outcome — correctly weighting each contribution by both its size and exactly how long it had to grow. This is the correct way to measure the real annualized return of a SIP, a series of lumpsum top-ups, or any investment with cash flows on irregular dates.

Worked example — Why a SIP's 'return' isn't just its assumed rate

A SIP run at an assumed 12% annual return doesn't actually deliver a flat 12% XIRR in the real world, because each month's contribution compounds for a different length of time and actual monthly market returns vary. The 12% used in a SIP calculator is an assumed constant rate for projection purposes; the XIRR calculated afterward, from real contribution dates and real market movements, is what your investment actually delivered — the two numbers are related but not identical, and checking your real XIRR periodically is the honest way to know how an ongoing SIP is actually performing.

Common mistakes

Using a simple CAGR calculation (start value vs. end value) to judge the performance of a SIP or any investment with multiple contribution dates.
Assuming a SIP calculator's assumed rate (e.g. 12%) is the exact return actually being delivered, rather than a planning assumption.
Comparing one investment's XIRR to another's CAGR as if they were the same measurement — they answer the same underlying question but aren't interchangeable for irregular cash flows.

Frequently asked questions

What's the difference between XIRR and CAGR?

CAGR assumes one investment made on one date and withdrawn on another. XIRR handles multiple cash flows on different dates — the realistic case for a SIP, top-ups, or partial withdrawals — correctly weighting each by size and how long it grew.

Why doesn't a SIP's actual return match its assumed rate exactly?

The assumed rate (e.g. 12%) is a planning assumption for projection purposes. The real XIRR, calculated from actual contribution dates and actual market movements, reflects what really happened and will differ from the flat assumption.