Compound Interest Calculator
Simulate long-term investment growth with monthly contributions and annual compound interest.
How to Use the Compound Interest Calculator
- Enter your parameters: Type, paste, or select your input values above.
- View instant results: Calculations update in real time as you change values.
- Copy or export: Click copy, download, or print to use your results immediately.
About this Tool
See how your wealth grows over time with compound interest. Supports daily, monthly, quarterly, and annual compounding with recurring deposits.
Compound Interest Growth Formula
Future Value (A) = P * (1 + r/n)^(n*t) + PMT * [((1 + r/n)^(n*t) - 1) / (r/n)]Compound interest generates exponential growth because interest earned in each compounding cycle is reinvested into the principal balance, earning its own interest in subsequent periods.
Worked Example: 10-Year Index Fund Investment Example
$10,000 Initial Principal, $200 Monthly Contribution, 7.5% Annual Return, Compounded Monthly for 10 Years
$56,402.73 Total Balance ($34,000 Contributed, $22,402.73 Interest Earned)
Interest compounding accelerates after year 5, where compound earnings begin to outpace annual cash contributions.
Frequently Asked Questions
What is the Rule of 72 mental shortcut?
Divide 72 by your annual interest rate to estimate how many years it will take an investment to double. At an 8% annual return, your money doubles in approximately 72 / 8 = 9.0 years.
How does daily compounding differ from monthly compounding?
Daily compounding applies the interest rate divided by 365 days every single day. Over long periods, daily compounding generates slightly higher effective annual yields (APY) than monthly compounding.
What is the difference between APR and APY?
APR (Annual Percentage Rate) is the stated nominal rate without compounding. APY (Annual Percentage Yield) accounts for compounding frequency and reflects the real percentage return earned over one year.
Calculation Standards
Complies with US Truth in Savings Act (TISA) and SEC compound growth disclosure standards. For tax, legal, or medical advice, consult certified professionals.
Related Practical Guide
Learn the exact mathematical formula to calculate percentage increase and decrease between two numbers. Includes worked financial examples, negative number handling, and Excel syntax.
Read tutorial →Understand how compound interest accelerates wealth accumulation. Discover the exact compounding formulas, how monthly compounding differs from annual, and how to project investment returns.
Read tutorial →Step-by-step mathematical guide to calculating monthly fixed-rate mortgage payments. Learn how amortization curves work, how property tax and insurance affect PITI, and how extra principal payments slash interest.
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