Interest & Loan Calculator

Calculate simple interest, compound interest, loan payments, and compare financial plans

Simple Interest
Compound Interest
Loan Calculator
Compare Plans

Share Your Calculation

Educational Note

The Interest Calculator provided on 21K Tools is designed for educational and informational purposes only. It helps students, learners, and individuals understand how simple and compound interest are calculated in mathematics and finance.

Complete Guide to Interest & Loan Calculations

Managing finances is a daily part of life, whether you are saving for the future, paying off a loan, or just curious about how interest grows over time. To make this process easier, 21K Tools offers a free Interest & Loan Calculator – a powerful, browser-based tool that helps you calculate simple interest, compound interest with contributions, loan payments, and even compare multiple financial plans.

Why Do You Need an Interest & Loan Calculator?

Finance may look complicated at first glance, but at its core, it comes down to three main elements: principal amount, interest rate, and time. Whether you are depositing money into a savings account, investing in a scheme, or borrowing from a bank, interest is always involved.

Simple Interest Calculator

Simple interest is the most basic form of interest. It is calculated using the formula:

SI = (Principal × Rate × Time) / 100

For example, if you deposit ₹10,000 at 5% annual interest for 3 years, you'll earn ₹1,500 as interest.

Perfect for:

  • Short-term deposits and savings accounts
  • Educational projects and learning
  • Quick financial calculations
  • Understanding basic interest concepts

Compound Interest Calculator

Compound interest is often called the eighth wonder of the world because it makes money grow exponentially. Unlike simple interest, compound interest adds earned interest back into the principal.

A = P(1 + r/n)^(nt)

Where:

  • A = Total amount
  • P = Principal
  • r = Interest rate (decimal)
  • n = Compounding frequency per year
  • t = Time in years

Features:

  • Multiple compounding frequencies (Daily to Annually)
  • Regular contribution options (like monthly SIPs)
  • See how contributions accelerate growth
  • Ideal for long-term investment planning

Loan Calculator

Understanding monthly payments (EMIs) and total repayment cost is crucial before borrowing. The tool uses the standard EMI formula:

EMI = [P × r × (1+r)^n] / [(1+r)^n – 1]

Features:

  • Calculate EMI for home loans, car loans, personal loans
  • Choose payment frequency (Monthly, Bi-Weekly, Weekly)
  • View detailed amortization schedule
  • See breakdown of principal vs interest for each payment
  • Understand total interest paid over loan term

Compare Financial Plans

Sometimes you have multiple options with different interest rates. Our comparison tool helps you:

  • Compare two investment or loan schemes side by side
  • See the exact difference in returns or costs
  • Identify which plan is better for your situation
  • Make informed financial decisions

How to Use Each Calculator

Simple Interest Calculator

  1. Enter your Principal Amount
  2. Enter the Annual Interest Rate (in percentage)
  3. Enter the Time Period
  4. Select the Time Unit (Days, Months, or Years)
  5. Choose your preferred Currency
  6. Click "Calculate Simple Interest"

Compound Interest Calculator

  1. Enter the Principal Amount
  2. Enter the Annual Interest Rate
  3. Enter the Time Period in years
  4. Select Compounding Frequency
  5. Enter Regular Contribution (optional)
  6. Select Contribution Frequency
  7. Click "Calculate Compound Interest"

Loan Calculator

  1. Enter the Loan Amount
  2. Enter the Annual Interest Rate
  3. Enter the Loan Term in years
  4. Select Payment Frequency
  5. Click "Calculate Loan Payment"
  6. Optionally view the Amortization Schedule

Compare Plans

  1. Enter the Principal Amount
  2. Enter interest rates for Plan 1 and Plan 2
  3. Enter the Time Period
  4. Click "Compare Plans"

Key Benefits

  1. All-in-One Solution – Four calculators in a single platform
  2. Multi-Currency Support – Calculate in USD, EUR, GBP, JPY, or INR
  3. Shareable Results – Download calculations as images
  4. Amortization Schedule – Detailed payment breakdown for loans
  5. No Registration Required – 100% free and instant access
  6. Mobile Friendly – Works perfectly on all devices
  7. Privacy Protected – All calculations happen in your browser

Practical Use Cases

Frequently Asked Questions

What is the difference between simple and compound interest?

Simple interest is calculated only on the principal amount throughout the investment period. The formula is: SI = (P × R × T) / 100.

Compound interest includes both the principal and accumulated interest from previous periods, leading to exponential growth. It's calculated using: A = P(1 + r/n)^(nt).

For example, ₹10,000 at 10% for 5 years:

  • Simple Interest: ₹5,000 interest (Total: ₹15,000)
  • Compound Interest (Annual): ₹6,105 interest (Total: ₹16,105)
Can I use this calculator for student loans?

Yes! The Loan Calculator works for all types of loans including student loans, home loans, car loans, and personal loans. Simply enter:

  • The total loan amount you're borrowing
  • The annual interest rate offered by the lender
  • The repayment period (tenure) in years
  • Your preferred payment frequency

The calculator will show you the exact payment amount per period, total interest you'll pay, and overall cost of the loan.

How accurate are the calculations?

Our calculations use standard financial formulas and are mathematically accurate. However, please note:

  • Real-world interest rates may include additional fees, taxes, or charges
  • Banks may use slightly different calculation methods
  • This tool is for educational and planning purposes
  • Always verify final numbers with your financial institution
What is an amortization schedule?

An amortization schedule is a detailed table that shows the breakdown of each loan payment into:

  • Payment Number: Sequential payment periods
  • Payment Amount: Total EMI paid
  • Interest Portion: Amount going toward interest
  • Principal Portion: Amount reducing the loan balance
  • Remaining Balance: Outstanding loan amount

This helps you understand how your loan gets paid off over time. Early payments have more interest, while later payments have more principal.

Is this calculator free to use?

Yes! The Interest & Loan Calculator by 21K Tools is completely free to use with no hidden charges, subscriptions, or registration required. You can:

  • Perform unlimited calculations
  • Access all four calculator types
  • Download and share your results
  • Use it on any device (phone, tablet, computer)
Which currencies are supported?

We currently support five major currencies:

  • USD ($) - US Dollar
  • EUR (€) - Euro
  • GBP (£) - British Pound
  • JPY (¥) - Japanese Yen
  • INR (₹) - Indian Rupee

You can switch between currencies anytime using the currency selector in the results section.

Can I save my calculations?

Yes! You can download your calculation results as an image using the "Share" button. This creates a professional-looking card with:

  • All your input values
  • Complete calculation results
  • Timestamp of calculation
  • 21K Tools branding

You can save these images for your records or share them with others.

Conclusion

The Interest & Loan Calculator by 21K Tools is your comprehensive financial planning companion. Whether you're learning about interest, planning investments, comparing loan options, or making important financial decisions, this tool provides accurate, instant calculations in an easy-to-use interface.

Start calculating now and take control of your financial future!

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