Compound Interest Calculator
Project savings or investments with compound interest and regular contributions.
Savings plan
Final value
Year by year
| Year | Contributions | Interest | Balance |
|---|
Runs entirely in your browser. Nothing you enter is uploaded.
Compound vs simple interest
Simple interest is paid on the original amount only, so NT$100,000 at 5% earns NT$5,000 every year. Compound interest is paid on the balance including the interest already added: the second year earns 5% of 105,000, the third 5% of 110,250, and the curve bends upward. This calculator turns the rate you enter into an equivalent monthly rate for the compounding frequency you choose, then steps through every month, adding your regular contribution at the start or end of each period, so the yearly table and the final value stay consistent whatever options you combine.
Frequency matters a little, time matters a lot
Compounding more often helps, but less than most people expect: NT$100,000 at 5% for 10 years grows to 162,889 compounded yearly and 164,701 compounded monthly, a gap of under 2,000. Doubling the time, on the other hand, roughly squares the growth: the same deposit left for 20 years reaches about 265,330. The rule of 72 (72 ÷ rate ≈ years to double) is a quick way to feel this, and the exact figure is shown next to it.
Example and notes
- Regular investing (定期定額): NT$5,000 a month at 6%, compounded monthly, for 20 years means you put in 1.2 million and end with about 2.31 million.
- The inflation field divides the final value by (1 + inflation)^years to show its buying power in today's money.
- Taiwanese savings accounts usually compound monthly or quarterly; a time deposit (定存) only compounds if you pick 整存整付, while 存本取息 pays simple interest.
- The rate is applied exactly as entered; taxes such as the supplementary health insurance premium on large interest payments, fees and fund costs are not deducted.
Privacy
Everything is calculated on your device. The amounts you enter are never sent to a server or stored.