About the emi calculator
An EMI is a fixed monthly payment that clears a loan over its term. The formula is standard, but the number people should actually look at is not the EMI — it is the total interest, and how the split between interest and principal changes over time.
This calculator uses the reducing-balance method, where interest each month is charged only on the outstanding principal. That is how home, car and personal loans work in India. It is worth distinguishing from a flat rate, where interest is charged on the original amount for the entire term: the same number quoted flat costs substantially more, which is exactly why some lenders quote it that way.
The amortisation schedule is the part worth reading. Early in a long loan almost the whole payment is interest — on a twenty-year home loan the first instalment might put barely a fifth toward principal. That is why paying a little extra in the early years shortens the loan far more than the same amount later, and why the outstanding balance barely moves for the first few years.
The schedule is grouped by year and expands to individual months. Rounding is absorbed in the final payment so the balance lands exactly on zero rather than a few paise adrift, which is what your lender's own schedule will do too.
Prepayment is not modelled here. It changes the shape of the loan substantially and deserves a tool of its own rather than a checkbox. As a rule of thumb, a prepayment in year two of a twenty-year loan saves several times what the same amount saves in year fifteen.