See how savings or investments grow with compound interest and regular contributions. Enter the details below.
Usage Tip
The Rule of 72: divide 72 by the rate to estimate years to double. At 8%, money doubles in about 9 years.
plus contributions compounded each period
r = annual rate, n = times compounded per year, t = years
More frequent compounding (monthly versus annually) helps slightly; the rate and time matter far more.
Real returns vary year to year; this assumes a steady rate, so treat it as a smooth estimate.
Inflation reduces what the future balance can buy; a separate inflation calculation shows the value in today dollars.
Compound interest means that interest is added to the balance and then earns interest itself. Over time this produces growth that speeds up, unlike simple interest, which is only paid on the original amount. The final balance depends on the amount, the rate, how often interest compounds, and how long the money is left to grow.
More frequent compounding gives a slightly higher result for the same rate, but time and the rate itself matter much more. A handy approximation is the rule of 72: divide 72 by the annual rate to estimate how many years it takes to double, so 6 percent doubles in about 12 years. The same math works against you on debt, where interest also compounds.