How this calculator works
Enter principal, the bank’s published or contracted annual rate, months per term and renewal count. The renewal scenario reuses the entered rate so different terms can be compared.
Calculation method
Each term earns opening balance × annual rate × months ÷ 12. On renewal, principal and interest become the next term’s opening balance and the rate is assumed unchanged.
Check before using the estimate
The page compares fixed-rate, whole-month maturity and renewal scenarios. Use the deposit contract for actual-day counting, value dates, the renewal-day rate, early withdrawal and deposit-insurance eligibility.
Worked example
Example input: principal ¥100,000, annual rate 2.00%, 12-month term, 1 automatic renewal.
| Period | Opening | Interest calculation | Interest | Ending |
|---|---|---|---|---|
| Period 1 | ¥100,000 | ¥100,000 × 2% × 12 ÷ 12 | ¥2,000 | ¥102,000 |
| Period 2 | ¥102,000 | ¥102,000 × 2% | ¥2,040 | ¥104,040 |
| Total | — | — | ¥4,040 | ¥104,040 |
Compared with two single periods without renewal: ¥2,000 × 2 = ¥4,000, ¥40 less — that ¥40 is the compounding from interest turning into principal. The default scenario has no renewal and a blank rate; the user must enter the actual bank rate.
Input variations
| Change | Ending value | Total interest | vs default |
|---|---|---|---|
| Add 5 renewals (6 periods, 6 years at 2%) | ≈ ¥112,616 | ≈ ¥12,616 | Compounding more pronounced |
| Switch to 24-month term (2.50% scenario) | ¥105,000 | ¥5,000 | Longer single period, higher rate |
| Early withdrawal at a 0.20% scenario rate | ≈ ¥100,400 | ≈ ¥400 | Far below term deposit |
Actual bank interest is computed on actual days, so the whole-month approximation differs by 1–3 days of interest; automatic renewals use the bank's posted rate on the renewal date, while this tool assumes the rate stays constant.
Differences from official documents
Differences from actual bank interest arise because: actual-day counting uses 365/360 or actual days, and whole-month approximation differs by 1–3 days of interest; value dates and maturity dates are bank-confirmed, not the user-input dates; automatic renewals use the bank’s posted rate on the renewal date, while this tool assumes the rate stays constant — actual rates fluctuate; large certificates of deposit, structured deposits and negotiated deposits have different interest rules and this tool does not apply; early withdrawal uses the current account rate or a residual-term deposit rate, varying by jurisdiction.
Thresholds and limits
Principal > ¥0; annual rate 0%–50% (required, blank produces no result); term 1–120 months; renewals 0–20; no default rate — enter the bank’s actually posted rate to avoid using outdated national unified rates. Deposit insurance covers ¥500,000 of principal (with interest combined), but this tool does not compute insurance payouts.
Documents to check
Bank term deposit certificate or deposit receipt; bank app or online banking deposit detail (showing value date, maturity date, rate); bank posted-rate announcement (confirm the rate at the time); automatic renewal agreement or deposit contract terms; early withdrawal application and bank-issued interest list (if applicable); large certificate of deposit or structured deposit product information sheet (if applicable).
Renewal-date rate and day-count rules drive real renewals
The page holds one entered rate constant so the scenario remains reproducible.
Each term uses simple interest first
Principal and interest join only at maturity, creating compounding between renewal cycles.
Automatic renewal does not preserve the old rate
The bank contract controls the maturity-day rate, value date, early withdrawal and insurance eligibility.
Primary source
People’s Bank of China (policy context; use the bank contract rate)