NPS works differently from a fixed-return savings product: instead of a guaranteed interest rate, your contributions are invested across a mix of asset classes you select, and the corpus grows based on how those investments actually perform over your working years. Understanding the two separate mechanics, how the corpus accumulates and how it's eventually paid out, explains why NPS projections are always estimates rather than guaranteed figures.
How the accumulation phase works
During the accumulation phase, regular contributions (yours, and often a matching employer contribution) are allocated across asset classes, typically equity, corporate bonds, and government securities, in proportions you can usually adjust within regulatory limits. Because equity and bond returns vary year to year, the corpus doesn't grow at a fixed rate the way a fixed deposit does, it compounds at whatever the underlying investments actually return, which historically trends higher than fixed-income products over long horizons but with more year-to-year variability.
This is why the NPS Calculator works with an assumed average annual return rather than a guaranteed one, projecting the corpus you'd accumulate under a chosen return assumption, contribution amount, and number of years remaining until retirement, while making clear that the actual outcome depends on real market performance over that period.
The annuity requirement at retirement
Unlike most other retirement or investment products, NPS doesn't let you withdraw the entire accumulated corpus as a lump sum at retirement. A portion (commonly a minimum of 40%) must be used to purchase an annuity, a financial product that converts that portion into a regular pension payment for the rest of your life, while the remainder can typically be withdrawn as a lump sum, often tax-free up to a limit. This split matters for planning because the annuity portion's ongoing payout rate is separate from, and usually lower than, the growth rate the corpus achieved during accumulation.
Because the mandatory annuity portion locks in a fixed pension rather than continuing to grow at market rates, NPS functions as a hybrid: a market-linked growth phase followed by a guaranteed-income phase, which is a meaningfully different structure from a pure retirement investment account that stays fully liquid at maturity.
Where NPS fits alongside other retirement savings
NPS is generally most useful as one part of a broader retirement plan rather than the sole vehicle, precisely because of the mandatory annuitization and its own contribution limits. Comparing an NPS projection against a broader retirement savings target, one that also accounts for other investments, is worth doing on the Retirement Calculator, which projects overall corpus needs against expected expenses in retirement, independent of any single product's specific rules.