How it works
The target comes from two numbers you choose. Annual spending divided by your withdrawal rate gives the corpus: a 4% rate implies 25 times spending, a 3% rate implies about 33 times. The multiple is a consequence of your assumption, not a rule this calculator applies.
Accumulation then runs forward month by month on the **real** return — your return assumption net of your inflation assumption. This matters more than it sounds: the target is expressed in today's spending, so growing the corpus at a nominal rate would compare a future-rupee corpus against a today-rupee target and overstate progress considerably.
More detail
The calculator also reports the monthly amount that would reach the target over the same horizon, given what you already hold, so you can see the gap between what you are doing and what the target implies.
When the target is not reached within 60 years the calculator says so rather than showing a misleading figure.
To model drawing from the corpus once you get there, use the SWP calculator.
Because spending drives both the target and what you can invest, the savings rate calculator.