The full guide
CAGR Explained: The Honest Way to Talk About Investment Growth
Reviewed and updated July 16, 2026 · Written for Sri Lankan investors and borrowers
When someone says their CSE portfolio “doubled in five years”, the useful question is: what does that mean per year? The compound annual growth rate answers it. CAGR is the single steady yearly rate that would carry your starting value to your ending value over the period, smoothing out all the ups and downs in between. It is the standard language for comparing investments over different time spans.
This guide shows how CAGR is calculated, works through examples in rupees, and, just as importantly, explains the situations where CAGR misleads and a different measure, XIRR, is the honest tool.
The formula and a worked example
CAGR equals the ending value divided by the beginning value, raised to the power of one over the number of years, minus one. If Rs 100,000 invested in a CSE stock grows to Rs 200,000 in five years, CAGR is 2 raised to the power of one fifth, minus 1, which is about 14.9 percent a year. The doubling did not happen smoothly, but 14.9 percent is the constant rate that produces the same end result, and it lets you compare this outcome against an FD, a unit trust or any other option quoted in annual terms.
Why the same total return can mean very different CAGRs
Time is everything in compounding. A 50 percent total gain sounds identical whether it took two years or ten, but the annualized picture differs enormously, as the table shows. This is why quoting total returns without the holding period, a favourite habit of investment marketing everywhere, tells you almost nothing.
| Holding period | Total gain | CAGR |
|---|---|---|
| 2 years | 50 percent | about 22.5 percent per year |
| 5 years | 50 percent | about 8.4 percent per year |
| 10 years | 50 percent | about 4.1 percent per year |
When CAGR works well
CAGR is the right tool when there is a single sum at the start, no money added or withdrawn along the way, and a value at the end. Comparing a five-year FD against five years of holding a unit trust with one initial investment, measuring how a company’s revenue grew across several years, or checking a fund fact sheet’s annualized figure are all natural CAGR territory.
It also cuts through cherry-picked marketing. A fund boasting 300 percent growth “since inception” fifteen years ago has a CAGR of about 9.7 percent a year, a figure you can instantly weigh against everything else available to you.
When CAGR misleads, and where XIRR takes over
CAGR hides volatility completely. A portfolio that crashed 50 percent and then recovered shows the same CAGR as one that grew serenely, yet the lived experience and the risk were entirely different. It is also acutely sensitive to its two endpoints: measure from a market bottom to a peak and the figure flatters wildly; shift either endpoint a year and the story changes.
Most importantly, CAGR is simply wrong for the way real people invest, adding money monthly, withdrawing for emergencies, topping up when markets fall. Applying the CAGR formula to a portfolio with contributions treats your own deposits as investment growth. For any cash-flow pattern with multiple dates, XIRR is the correct measure, and our XIRR calculator handles exactly that case.
Practical habits for Sri Lankan investors
Always annualize before comparing, always ask over what period a return was earned, and always check whether money moved in or out during that period. When evaluating CSE stocks or unit trusts, look at CAGR across several distinct multi-year windows rather than one flattering stretch, and remember that past CAGR describes history, not a promise about the future.
One more habit worth building: compute CAGR in real terms occasionally. A 12 percent nominal CAGR during years of high inflation may represent little or no growth in purchasing power, while an 8 percent CAGR in a low-inflation stretch can be genuinely excellent. Pair this calculator with our inflation calculator to see both sides of the story, and judge every long-term result by what it lets you actually buy.
Use matching, total-return endpoints. The starting value should be immediately after the investment and the ending value should include cash dividends or distributions unless the published series already assumes reinvestment. Adjust share quantities and prices consistently for splits, rights issues, bonus issues, and major capital returns; otherwise a corporate action can appear as investment growth or loss. Record the exact dates rather than rounding a 20-month holding to two years, and compare like with like — after fees and tax on both alternatives, in the same currency, across the same dates. Keep the source statements beside the result so the number can be reproduced later.
Sources & further reading
This guide is educational and reflects publicly available rules and market conventions at the review date. Tax rates, bank rates, and regulations change — verify current figures with the institution or the Inland Revenue Department before making a financial decision. Nothing here is financial, tax, or investment advice.