Bank FD screens show a rate and a maturity. They rarely show the compounding convention in the same font. The FD calculator uses A = P(1 + r/n)nt with n defaulting to 4 (quarterly). That is the code. If your deposit is monthly compounding, change n. If your deposit pays interest out every quarter and you spend it, you are not on this curve at all.
Cumulative versus payout
Cumulative: interest stays inside and earns interest. The yearly table shows a rising value. Payout: you receive interest as cash. Maturity is roughly the principal (plus any residual), and the “return” lived in your savings account, where it may have earned 3% and been spent on groceries. Comparing a payout FD to a SIP corpus is an accounting error. Comparing a cumulative FD to a SIP is still a risk-and-tax comparison - SIP vs FD but at least both are piles.
Why the bank slip disagrees
- Senior-citizen extra 0.5% you did not type.
- Monthly versus quarterly compounding.
- Interest payout vs cumulative.
- Premature-break penalty, which this tool does not model.
- TDS leaked from the compounding base.
Type the rate from the advice letter, not from a comparison website’s “best FD” table. Those tables mix tenures and payout styles. The RD calculator is the fair cousin when money arrives monthly; an FD is usually a lumpsum. A stack of small FDs from salary is closer to RD than to one five-year cumulative FD.
Inflation and tax sit outside
I did not auto-deflate FD maturity. A 7% cumulative FD at 6% inflation is a thin real result after slab tax. Do that subtraction yourself, or read the real column on the SIP tool as a contrast, not as a like-for-like product. DICGC insurance, premature withdrawal rules, and auto-renewal at a new rate are bank features. The calculator will not know you auto-renewed into a worse card.
If a relationship manager’s “₹X at maturity” and this page differ by a few rupees, rounding and day-count win for the bank. If they differ by lakhs, you are probably on payout versus cumulative, or a different n.