Interest Calculator

This calculator computes compound interest on an initial investment with optional periodic contributions. It accounts for compounding frequency (daily to annually), tax on earned interest, and displays the inflation-adjusted real value of your ending balance. Use it to plan savings goals, compare investment scenarios, or estimate retirement growth.

Frequently Asked Questions

What is compound interest?

Interest earned on both the initial principal and previously accumulated interest. It grows exponentially over time, unlike simple interest.

How does compounding frequency affect growth?

More frequent compounding (daily vs. annually) means interest is calculated and added more often, resulting in a slightly higher ending balance.

What is inflation-adjusted balance?

The real purchasing power of your ending balance after accounting for inflation. A $50K balance at 3% inflation is worth less in today's dollars.

When should I add annual contributions?

Regular contributions dramatically accelerate growth through compounding. Even small yearly additions compound significantly over 10–30 years.