What is the difference between simple and compound interest?

Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus accumulated interest — interest earns interest. Over long periods, compound interest grows exponentially faster.

What is the Rule of 72?

The Rule of 72 estimates how long it takes to double an investment: divide 72 by the annual interest rate. At 8% annual return, an investment doubles in approximately 72 ÷ 8 = 9 years.

APR (Annual Percentage Rate) is the simple annual rate. APY (Annual Percentage Yield) includes the effect of compounding within the year. A 12% APR compounded monthly equals a 12.68% APY.

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Interest Calculator

Name: Interest Calculator
Rating: 4.8 (120 reviews)
Author: DailyDevTools

Simple vs Compound interest calculator

Principal ($)

Interest Rate (%)

Time Period (Years) (10 Years)

Type

Compound Frequency

Total Value

Total Interest

Year 1Year 10

Principal

Interest

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What is Interest Calculator?

Understanding how interest grows your savings or increases your debt is fundamental to personal finance. DailyDevTools' Interest Calculator handles both simple interest (I = P × r × t) and compound interest with configurable compounding frequency (daily, monthly, quarterly, annually) and shows a year-by-year growth chart so you can visualize the power of compounding over time.

How to use Interest Calculator

1Enter the principal amount, annual interest rate, and time period
2Choose interest type: Simple (flat rate) or Compound
3For compound interest, select the compounding frequency: daily, monthly, quarterly, or annually
4View total interest earned, final balance, and the year-by-year growth table

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