Compound interest pays interest on the interest already earned, which is why money left to grow accelerates rather than rising in a straight line. Enter a starting amount, an optional regular contribution, the annual rate, how often interest is added and the number of years; the calculator shows the final value, how much of it is contributions and how much is growth, and a year-by-year table. An inflation rate turns the result into today's purchasing power, which is the honest way to judge a long-term plan.
Compound Growth Calculator
Compound growth applies each period's return to the previous balance, so growth accelerates over time. The compound growth calculator takes a starting amount, a monthly contribution, an annual return and a number of years, and lets you choose how often interest is compounded. $10,000 plus $200 a month at 7% compounded monthly grows to about $54,700 in ten years, of which $34,000 is money you put in and about $20,700 is growth.
Add an inflation rate and the calculator also shows what the final balance is worth in today's money, which is the number that matters for a savings goal. The year-by-year table separates contributions from earnings so you can see the point at which the growth starts to outpace what you add.
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Frequently Asked Questions
What is the compound interest formula?
A = P × (1 + r ÷ n)^(n × t), where P is the principal, r the annual rate, n the compounding periods per year and t the years. Regular contributions are added each period before compounding.
Does compounding frequency matter much?
Less than people expect. At 7% a year, $10,000 grows to $19,672 with yearly compounding and $20,097 with monthly compounding over ten years. The rate and the time matter far more.
What is the rule of 72?
A quick estimate of doubling time: divide 72 by the annual rate. At 8% money doubles in about 9 years. The calculator gives the exact figure.
