XIRR vs. CAGR: Your SIP App Might Be Showing You the Wrong Return

Ask most people what return their SIP is earning and they'll quote a "CAGR" number from their investing app. For a lump sum investment, CAGR is exactly right. For a SIP — where you're putting in different amounts of money on different dates — CAGR is the wrong formula, and it can meaningfully mislead you about how well your money is actually growing.

What CAGR actually measures

CAGR (Compound Annual Growth Rate) answers one specific question: if I invested a single amount once, and it grew to this final value over this many years, what constant annual growth rate would explain that?

CAGR = (Final Value / Initial Value)^(1/years) − 1

This formula assumes exactly one cash flow, on exactly one date. It has no concept of "money invested in month 3" versus "money invested in month 30" — it just compares a starting number and an ending number.

Why that breaks for a SIP

A SIP isn't one investment — it's dozens or hundreds of separate investments, each made on a different date, each of which has been growing for a different amount of time. Money invested in your first month has had the full period to compound; money invested last month has barely had any time at all. Collapsing all of that into a single "initial value vs final value" CAGR calculation doesn't match what actually happened to your money.

Depending on how your app estimates an "equivalent initial value" for a SIP, this can distort the number in either direction — sometimes making a SIP look like it earned more than it really did, sometimes less, especially in a volatile market where the fund's price swung a lot between your contribution dates.

What XIRR does differently

XIRR (Extended Internal Rate of Return) is built for exactly this situation: multiple cash flows, on different dates, of different amounts. It finds the single annualized rate of return that makes the present value of every individual contribution — each dated and sized correctly — equal to your current portfolio value. Every SIP installment is treated as its own cash flow with its own start date, so a contribution from 3 years ago is correctly weighted as having compounded for 3 years, while last month's contribution is correctly weighted as having compounded for almost no time at all.

This is why every serious SIP or portfolio return calculation — including the ones brokers and portfolio trackers use internally — is XIRR, not CAGR. If an app shows you a single "returns" percentage on a SIP without specifying which formula it used, there's a real chance it's quietly using something closer to CAGR logic and giving you a distorted number.

A concrete case where the two diverge sharply

Say you SIP ₹10,000/month for 3 years, and in year 1 the market fell 20% before recovering fully by year 3. A naive CAGR-style calculation comparing total invested vs. final value can undercount how well your later, larger contributions (made after the fund's price had already recovered) actually performed — because it doesn't distinguish when each rupee went in. XIRR correctly credits each contribution based on its actual entry price and actual holding period, which is the entire reason it exists.

The practical takeaway

For a lump sum investment, CAGR and XIRR give you the same answer — no issue there.
For any SIP, recurring investment, or portfolio with contributions and withdrawals on different dates, only trust a return number if you know it's XIRR.
Most reputable mutual fund platforms label their SIP return correctly as XIRR — if a number is just labeled "returns" with no formula specified, treat it with some skepticism, especially for volatile fund categories where the gap between CAGR-style and XIRR calculations widens the most.

Check your own SIP math

Our Investment Goal Calculator projects your SIP forward using the same monthly-compounding logic that underlies a proper XIRR calculation, so the numbers you plan against match how your actual returns will be measured later.