XIRR vs CAGR — Which One Actually Measures Your SIP Returns Correctly
If you've ever checked your SIP's "returns" on two different platforms and gotten two noticeably different numbers, the most likely explanation isn't a data error — it's that one platform used CAGR and the other used XIRR, and for a SIP, only one of these is actually the correct measure.
What CAGR Measures
Compound Annual Growth Rate (CAGR) measures the annualised growth rate of a single, lump-sum investment made at one point in time and held until another point in time. The formula is:
CAGR = (Ending Value ÷ Beginning Value)^(1 ÷ Number of Years) − 1
CAGR assumes exactly one cash inflow at the start and exactly one cash outflow (the final value) at the end — nothing in between. This makes it the right tool for measuring, say, a single lumpsum investment made three years ago and redeemed today.
Why CAGR Breaks Down for a SIP
A SIP, by definition, involves multiple cash flows at different points in time — a separate investment made every month (or week, or quarter), each with its own holding period until the valuation date. A unit purchased in month 1 has been invested far longer, and has had far more time to compound, than a unit purchased in month 36. CAGR has no way to account for this — it can only compare one starting amount to one ending amount over one uniform time period, which simply doesn't describe how a SIP actually works.
If you naively apply a CAGR-style calculation to a SIP by treating the sum of all instalments as a single "starting investment," you get a distorted, generally understated return figure, because it ignores the fact that most of your money was invested for a shorter period than the SIP's full duration and effectively averages the whole thing as though every rupee had been invested from day one.
What XIRR Actually Measures
Extended Internal Rate of Return (XIRR) is built precisely for this situation — it can handle multiple cash flows occurring on different, even irregular, dates, and calculates the single annualised rate of return that makes the present value of all those cash flows (each instalment, each redemption) equal to zero. In practice, this means XIRR correctly accounts for the fact that:
- Your first SIP instalment has been compounding for the full duration of the SIP.
- Your most recent instalment has barely had time to compound at all.
- Every instalment in between has had a proportionate amount of time to grow. XIRR effectively weighs each cash flow by exactly how long it has actually been invested, arriving at a single blended annualised return figure that genuinely reflects your real investing experience.
A Simple Illustration of Why This Matters
Suppose you invested ₹10,000 per month for 36 months (₹3,60,000 total invested), and your investment is worth ₹4,50,000 today.
- A naive CAGR-style calculation, treating the whole ₹3,60,000 as if it were invested on day one for the full 3 years, would significantly understate your actual annualised return, because in reality most of that money was invested for considerably less than 3 years.
- XIRR, by properly weighting each of the 36 individual monthly cash flows by its actual investment duration, produces the correct annualised return — which, in a scenario like this, is typically meaningfully higher than what a misapplied CAGR calculation would suggest. This is precisely why AMC and platform-reported SIP returns should always be — and typically are, when done correctly — XIRR figures, not CAGR figures.
When to Use Which
- Use CAGR for a single lumpsum investment made once and held to a specific end date — it's simpler, and it's the mathematically correct tool for that specific situation.
- Use XIRR for any investment involving multiple cash flows at different times — SIPs, STPs, or any portfolio where you've added or withdrawn money at various points, since it's the only measure of the two that correctly accounts for the differing time each rupee has been invested.
A Related Trap: Confusing "Absolute Return" With Either
A third, even simpler (and often more misleading) figure sometimes shown is absolute return — simply (current value − invested amount) ÷ invested amount, with no annualisation at all. This tells you the total percentage gain over the entire period, regardless of whether that period was six months or six years, and cannot be meaningfully compared across investments held for different durations. Absolute return is not a substitute for either CAGR or XIRR — it answers a genuinely different question ("how much did I gain in total") rather than "at what annualised rate did my money grow."
Why This Matters
For anyone running a SIP — which is how the large majority of Indian mutual fund investors actually invest — XIRR is the only measure that correctly reflects the reality of periodic, staggered investing. Understanding this distinction isn't just academic: it explains why your SIP's "return" can look meaningfully different across two apps or statements, and it ensures you're evaluating your actual investing performance against the right yardstick rather than a mismatched or misapplied one.