Compound interest is interest earned on interest: each period, your gains are added to the balance and the next period is calculated on the new total. This calculator takes a starting balance, an annual rate, a compounding frequency and an optional monthly contribution, then shows the year-by-year growth in a table.
The formula is A = P·(1 + r/n)^(n·t), where n is the number of compounding periods per year. Over long horizons the effect is dramatic — a small monthly contribution can double the final balance of a decades-long investment.
Frequently asked questions
What is the difference between simple and compound interest?
Simple interest is always calculated on the original principal; compound interest is calculated on the growing balance, so it earns "interest on interest".
Does compounding frequency matter?
Yes. More frequent compounding (monthly vs yearly) yields slightly more, though the difference shrinks as rates fall.
Are monthly contributions included from month one?
Yes, contributions are added at the end of each month and start compounding in the following period.
中文说明
复利就是"利息生利息"：每期收益计入本金，下一期按新总额计息。本计算器支持初始本金、年利率、复利频率与可选的每月定投，并以逐年表格展示增长过程。
公式为 A = P·(1 + r/n)^(n·t)，其中 n 为每年复利次数。时间越长效果越惊人——长期投资中，一笔小额月供可以让最终余额翻倍。
常见问题
复利和单利有什么区别？
单利永远按原始本金计息；复利按不断增长的总余额计息，相当于"利滚利"。
复利频率有影响吗？
有。更频繁的复利（如按月对比按年）收益略高，但利率越低差距越小。
每月定投从第一个月就算复利吗？
是的，定投在每月月末计入，并从下一期开始参与复利。