Long-term planning

Interest Calculator

Calculate compound interest and final balance for any principal amount and time period. Use this Savings and investing tool to enter your numbers, review the result, and understand the key assumptions before making the next decision.

What you get
A focused calculator, clear explanation, common questions, and useful next tools.
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Result
Explanation
Common questions
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How this calculator works
The result depends on the numbers you enter and the assumptions shown below.

Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. The compounding frequency (daily, monthly, quarterly, annually) significantly affects the final amount — more frequent compounding means faster growth. The formula is A = P × (1 + r/n)^(n×t), where P is principal, r is annual rate, n is periods per year, and t is years.

Review the inputs carefully and treat the output as an estimate. For decisions involving money, taxes, health, law, or security, compare the result with trusted professional guidance when needed.

Frequently asked questions

What is the difference between compound and simple interest?

Simple interest is calculated only on the principal. Compound interest is calculated on principal plus accumulated interest, resulting in exponential growth over time. The difference becomes significant over long periods.

How much does compounding frequency matter?

Daily compounding earns slightly more than monthly, which earns slightly more than annual. For a 5% rate, the difference between annual and daily compounding is about 0.12% in effective annual yield — meaningful over decades but small short-term.