Financial Calculators
Compound Interest Calculator
Estimate compound interest growth from a starting amount, contributions, rate, and time.
Estimate how compounding and regular contributions can grow an amount over time.
Enter a starting principal, periodic contribution, annual interest rate, time period, and compounding frequency. The calculator estimates future value using compound growth, with contributions deposited at the end of each period. It assumes a steady rate and schedule and does not include fees, taxes, inflation, market losses, or changing rates. This private browser estimate is not financial, investment, or tax advice; your values are not uploaded or stored.
Frequently Asked Questions
Everything you need to know about this tool, how it works, and privacy.
What formula does the compound interest calculator use?
The calculator grows the starting principal by (1 + r ÷ n)^(n × t), where r is the annual rate as a decimal, n is compounding periods per year, and t is years. It adds the future value of end-of-period contributions using the same periodic rate.
How do contributions and compounding frequency affect the estimate?
Regular contributions add more money to the amount that can grow. More frequent compounding applies growth more often at the annual rate you enter, while the calculator treats each contribution as deposited at the end of its selected period.
What are the limitations of this compound interest estimate?
The estimate assumes a steady annual rate, consistent end-of-period contributions, and unchanged compounding frequency. It does not include fees, taxes, inflation, market losses, withdrawals, changing rates, or account rules. It is not financial, investment, or tax advice.
Do my balances and rates stay private?
Yes. The calculation and copy action run locally in your browser. CodeASystem does not upload or store the values you enter.