About the fd calculator
A fixed deposit is the simplest thing a bank sells, and the maturity figure is still surprisingly easy to get wrong. Indian banks compound quarterly, but only over quarters that have actually completed. Whatever days are left at the end — the residual period — earn simple interest on the accumulated balance, not another fraction of a compounding period.
Most calculators online ignore that. They apply the closed-form formula with a fractional exponent across the whole tenure, which is fine when the tenure is a whole number of quarters and wrong the rest of the time. Since banks sell deposits at 444 days, 555 days and other odd counts precisely because they are promotional, the wrong case is common rather than rare.
This calculator does it the way the bank does. Enter the tenure in years, months and days, and it counts the completed quarters from your deposit date, compounds those, and then applies simple interest across the remaining days on an actual/365 basis — 366 when the residual falls in a leap year. It shows you the split, so you can see exactly how many quarters completed and how many days were left over.
It also shows what the naive formula would have given you. Be clear about the size of that gap: on five lakh over 444 days at 7.25% it is about ten rupees, not thousands. The point is not that you are being cheated — it is that when you reconcile this against your bank's figure, the numbers should agree, and with the wrong method they never quite will. The direction is consistent, incidentally: fractional compounding of a partial period always yields slightly less than simple interest on it, so the correct method pays marginally more.
Compounding frequency is adjustable for banks and NBFCs that differ from the quarterly norm, and there is an optional TDS calculation. Tax thresholds change most years, so the rate and threshold are editable rather than baked in — check the current figures before relying on the net number.