Compound Interest Calculator

Calculate how your savings or investments grow over time with compound interest. See the power of compounding at different frequencies.

Initial Principal

$0.00

Total Contributions

$0.00

Interest Earned

$0.00

Final Amount

$0.00

Growth Over Time

Formulas Used

Compound Interest: $A = P {(1 + \frac{r}{n})}^{n t}$

Continuous Compounding: $A = P e^{r t}$

Recurring Contributions: $A = P {(1 + \frac{r}{n})}^{n t} + C (\frac{{(1 + r / n)}^{p} - 1}{r / n})$

Continuous Compounding with Contributions: $A = P e^{r t} + M (\frac{{(e^{r / 12})}^{m} - 1}{e^{r / 12} - 1})$

Where:

P = principal
r = annual interest rate as a decimal
n = compounding periods per year
t = time in years
e = Euler's number, approximately 2.71828
M = monthly contribution
C = contribution per compounding period, calculated from the monthly contribution as M × 12/n
p = completed compounding periods
m = completed months
A = final amount

How this compound interest calculator works

This compound interest calculator estimates how savings or investments grow over time when interest is added repeatedly to the balance. It supports different compounding frequencies, recurring monthly contributions, and continuous compounding to help visualize long-term financial growth.

Compound interest allows both the original principal and previously earned interest to continue generating returns. Over long time periods, this compounding effect can significantly increase the final balance compared to simple interest.

What you can calculate

Future investment value
Total contributions over time
Total interest earned
Growth from recurring monthly deposits
Effects of different compounding frequencies
Investment growth scenarios with variable interest rates

Inputs explained

Principal Amount – your starting balance or initial investment.
Monthly Contribution – recurring deposits added during the investment period, this can be zero if you want to calculate without contribution.
Annual Interest Rate – expected yearly return expressed as a percentage.
Compounding Frequency – how often interest is added to the balance, such as monthly, quarterly, or daily.
Time Period – total investment duration in years.
Interest Rate Variance Range – optional high and low growth scenarios used for the chart projection.

Compound interest formula

Standard compound interest is calculated using:

A = P(1 + r/n)^nt

Where:

A = final amount
P = principal investment
r = annual interest rate
n = compounding periods per year
t = time in years

Why compounding frequency matters

More frequent compounding generally increases the final investment value because interest is added and reinvested more often. Daily compounding usually produces slightly higher returns than monthly or annual compounding at the same nominal interest rate.

Continuous compounding represents the theoretical limit where interest is compounded constantly using the exponential growth formula:

A = Pe^rt

Example calculation

Suppose you invest $10,000 at a 7% annual return compounded monthly, while contributing an additional $200 each month for 20 years. The calculator estimates the final balance, total contributions, and total interest earned while also visualizing growth over time.