About the swp calculator
A systematic withdrawal plan is a SIP run backwards. Instead of paying in every month, you hold a corpus in a fund and take a fixed amount out of it, while whatever is left keeps growing. It is how most people actually draw an income from investments after they stop earning one.
The question this answers is not what your money grows to. It is how long it lasts. Above a certain withdrawal the corpus erodes, below it the corpus grows, and the line between those two outcomes is much less obvious than it looks — which is why the tool tells you the exact month the money would run out rather than only showing a closing balance.
Withdrawals here come out at the start of each month and the remainder grows for that month, matching the convention the SIP calculator uses on the other side. This is not a rounding detail. A corpus of ten lakh withdrawing ten thousand a month at twelve percent looks like break-even, because one percent of ten lakh is exactly ten thousand — but the money you take out never earns that month's growth, so the balance drifts down. True break-even needs about 10.1 lakh. Assuming otherwise is the single most common reason people over-estimate how long a corpus will last.
The yearly increase matters more here than in a SIP. A withdrawal that stays flat for twenty years is a withdrawal that loses roughly half its purchasing power over that time, so a plan built on a fixed rupee amount quietly plans for getting poorer. Raising it in line with inflation is the honest version, and the tool takes a percentage, a flat amount, or a different figure for each year.
What this does not model: expense ratio, exit load, and the capital gains tax you pay on each redemption — which is real, because every SWP withdrawal is a redemption. Sequence risk is absent too, and it is the biggest omission: a market fall in the first few years of withdrawing does far more damage than the same fall later, because you sell more units to raise the same rupees. Treat the output as arithmetic, not a plan.