FD Calculator.

How the math works

Compounding frequency does the heavy lifting.

A fixed deposit's headline rate is annualised, but how often the bank compounds determines what you actually receive at maturity. The general formula is M = P × (1 + r / n)^nt, where P is principal, r is the annual rate as a decimal, n is the number of compounding periods per year, and t is the tenor in years.

What actually varies is n. Most scheduled commercial banks compound cumulative FDs quarterly (n = 4). A handful of NBFCs and some bank products compound monthly (n = 12). If you chose the non-cumulative payout option (interest paid monthly, quarterly, half-yearly, or annually instead of reinvested), the math collapses to simple interest with the payout schedule on top.

For tenors below six months, banks typically pay simple interest regardless of the cumulative or non-cumulative election. The calculator above lets you set the frequency explicitly so the result matches your bank's product.

The number shown is pre-tax. TDS at 10% kicks in once your annual interest from a single bank crosses ₹40,000 (₹50,000 for senior citizens), and the full interest amount is taxed at your marginal slab.