🏠 Home›Finance›Interest Calculator
💰 Finance

📈 Interest Calculator

Calculate simple interest and compound interest on any amount. See exactly how much your money earns — or how much a loan costs you in interest.

✏️ Enter Your Values
✨ Your Result
Result
🦉Owl's Explanation
📈
Fill in the values on the left
and click Calculate! ✨

🤔 How Does This Tool Work?

Our Interest Calculator handles two types of interest:

Simple Interest: I = P × R × T

  • I = Interest amount
  • P = Principal (original amount)
  • R = Annual interest rate (as decimal)
  • T = Time in years

Compound Interest: A = P × (1 + R)ᵀ

  • A = Final amount (principal + all interest earned)
  • The interest earned each year is added to the principal for the next year
  • This creates exponential growth — especially powerful over long periods
📚 Related Article
How to Save Money Every Month — Even If You Earn a Little →
Read Article →
❓ FAQ
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 the interest already earned — meaning interest earns more interest. Compound interest grows much faster over time.
What does 'compounding frequency' mean?▼
Compounding frequency is how often interest is added to the principal. Our calculator uses annual compounding. More frequent compounding (monthly, daily) produces slightly higher returns.
Why is compound interest called the eighth wonder of the world?▼
Einstein (reportedly) called compound interest this because of its extraordinary power to grow money over time. A small amount invested early can grow to an enormous sum decades later simply through compounding.
How does compound interest differ from a savings account?▼
A savings account typically compounds interest monthly or daily, adding to your balance regularly. Our calculator shows annual compounding. The principle is the same — the more frequently interest compounds, the more you earn.
What is a good interest rate for savings?▼
It varies by country and economic conditions. In Sri Lanka, fixed deposit rates have ranged from 8% to 15% in recent years. Compare rates from multiple licensed banks to find the best return on your savings.
🔧 Related Tools
🏦
Loan / EMI Calc
Monthly payments
 🐷
Savings Calculator
Long-term growth
 %
Percentage Calc
Quick percentages
 💼
Salary Calculator
Take-home pay