Fixed Deposit Interest Calculator – Lump Sum & Monthly Savings

A lump-sum deposit places all the principal upfront and returns principal plus interest at maturity in a single payment; no additional deposits are allowed. A monthly savings plan adds a fixed amount each month, and the full accumulated principal plus interest is paid out at maturity. Because the full lump-sum principal earns interest from day one while monthly contributions accrue only from when they are deposited, lump-sum deposits generally yield more interest for the same total amount under the same rate and term.

The monthly saving interest formula is I = M × n × (n+1)/2 × monthly rate, which is equivalent to an average effective principal of M × (n+1)/2 — roughly half the full 12-month total. For a 12-month plan, the average effective balance is M × 6.5, only about 54% of the equivalent lump sum. That is why monthly saving interest is typically just over half that of a lump-sum deposit under the same rate and term.

Yes — the term is converted to a fraction of a year: 3 months = 3/12 = 0.25 year, 6 months = 6/12 = 0.5 year, and so on. These are then plugged into the formula I = P × r × (n/12). For example, ¥10,000 at 1.95% for 6 months: I = 10,000 × 0.0195 × 0.5 = ¥97.50.

This tool uses the standard simple-interest formula (lump sum) and arithmetic-series formula (monthly saving), matching most banks' conventions. Small discrepancies of a few cents can arise from differences in how banks round interest, whether they count exact days vs. calendar months, or if a rate change occurs mid-term. Always confirm the final interest amount with your bank before depositing.

Under current Chinese policy (in effect since October 2008), interest on personal savings deposits is temporarily exempt from individual income tax. The interest shown in this tool is therefore the take-home amount with no further deduction required. Always verify with the latest PBoC and SAT announcements for any policy changes.