Summary: Calculate Interest Free and Privately
An interest calculator works out how much interest a sum earns, or costs, over a period of time. This free interest calculator handles simple and compound interest. Enter the principal, the annual rate and the time in years or months, choose how often interest compounds, and it returns the total interest, the final amount, the effective annual rate and a year-by-year growth table you can download as PDF or CSV.
The calculator runs in your browser; nothing is uploaded (you can check the Network tab in DevTools). It keeps nothing between visits and works with nine currencies for display: INR, USD, EUR, GBP, AUD, CAD, SGD, AED and JPY. There is no conversion between them, so enter the amount in the currency you pick.
Simple interest is SI = (P × R × T) ÷ 100. Compound interest is A = P × (1 + r/n)^(n × t). For ₹1,00,000 at 8% for 5 years compounded yearly, A = 1,00,000 × 1.08^5 = ₹1,46,932.81. For single-method pages, see the simple interest calculator and the compound interest calculator.
Table of Use: Interest Calculation Examples
| Scenario | What you enter | Result |
|---|---|---|
| Default compound example | ₹1,00,000, 8%, 5 years, Compound, Yearly | Interest ₹46,932.81; total ₹1,46,932.81; effective rate 8.00% |
| Simple interest | ₹1,00,000, 8%, 5 years, Simple | Interest ₹40,000.00; total ₹1,40,000.00 |
| Daily compounding | ₹1,00,000, 8%, 5 years, Compound, Daily (365) | Interest ₹49,175.93; effective rate 8.33% |
| Quarterly compounding | ₹1,00,000, 8%, 5 years, Compound, Quarterly | Interest ₹48,594.74; effective rate 8.24% |
| Nominal vs effective | ₹1,00,000, 12%, 1 year, Compound, Monthly | Total ₹1,12,682.50; effective rate 12.68% |
| Time in months | 10,000 USD, 6%, 18 months, Compound, Monthly | Interest $939.29; total $10,939.29 |
| Ten-year comparison | 100,000 USD, 10%, 10 years | Interest: simple $100,000.00; compound (yearly) $159,374.25 |
Features
- Simple and compound. Switch Interest Type, and for compound choose Yearly, Half-Yearly, Quarterly, Monthly or Daily (365) compounding.
- Effective annual rate. For compound interest the panel shows the effective annual rate, so different compounding frequencies can be compared fairly.
- Years or months. The time can be decimal and goes up to 100 years (1,200 months). Switching units keeps the same duration.
- Year-wise Growth. A table lists the opening balance, interest earned and closing balance for each year, with a final partial year labelled in months or days.
- Amount Breakdown. A chart splits the total into principal and interest percentages.
- Formula Used. The formula appears with your own numbers filled in.
- PDF and CSV export. The CSV opens in Excel, Google Sheets or Numbers, and both files are made on your device.
- Amount entry. Commas are accepted only as thousands separators (100,000 or 1,00,000); a form like 12,5 is flagged instead of misread.
The calculator grows one lump sum with no deposits or withdrawals. It ignores tax and fees, and it is not a loan repayment schedule.
How to Use the Interest Calculator
- Pick a currency and type the Principal Amount.
- Enter the Interest Rate (% per annum).
- Enter the Time Period and choose Years or Months.
- Choose Simple or Compound, and for compound pick the Compounding Frequency.
- Read Total Interest, Total Amount and the Effective Annual Rate, check the Year-wise Growth table, then press CSV or PDF to export.
If you only know two dates, the date difference calculator gives the period. To model regular deposits, try the savings calculator or the investment calculator, and for a pension use the retirement calculator.
Who Can Use It
- Savers and deposit holders comparing what a fixed deposit or savings account pays under different compounding rules.
- Borrowers checking what simple interest on a private loan adds up to. For instalments, use the loan calculator, EMI calculator or mortgage calculator.
- Students and teachers who want to see simple and compound growth side by side. The percentage calculator helps with the arithmetic.
- Anyone who needs a record and wants a PDF or CSV of the year-by-year numbers.
FAQs
Which is better: simple or compound interest?
For savings and investments, compound interest is better because you also earn interest on earlier interest. For borrowing, simple interest costs less. At 10% a year for 10 years, 100,000 earns 100,000 in simple interest but about 159,374 in interest compounded yearly.
How does compounding frequency affect returns?
More frequent compounding gives a slightly higher return because interest starts earning interest sooner. At 8%, yearly, quarterly, monthly and daily compounding give effective annual rates of 8.00%, 8.24%, 8.30% and 8.33%. The gain shrinks as frequency rises, so yearly to monthly matters more than monthly to daily.
What is the difference between the nominal and the effective rate?
The nominal rate is the stated annual rate before compounding. The effective annual rate (EAR) includes compounding: EAR = (1 + r/n)^n − 1, where n is the compounding periods per year. For example, 12% compounded monthly is an EAR of about 12.68%. Compare EARs when products compound at different frequencies.
How is interest calculated on loans?
Most instalment loans, such as home and car loans, charge interest each period on the outstanding balance, which falls as you repay; an EMI or loan calculator models that. This calculator grows a single lump sum. Some short-term loans use simple interest on the original amount, so check your agreement.
How long does it take for money to double?
The Rule of 72 estimates it: divide 72 by the annual rate, so 8% doubles money in about 9 years. The exact figure with yearly compounding is 9.01 years. To check, enter 100,000 at 8% for 9 years, compounded yearly, and the Total Amount is about 199,900.
Can I enter the time in months or a part of a year?
Yes. Switch the time unit to Months, or type decimals such as 2.5 years. Switching the unit keeps the same duration, so 5 years becomes 60 months. The year-wise table shows a final partial year with its months, such as Year 3 (6 mo), and compound interest uses the exact fraction of a year.
Are the PDF and CSV exports free and private?
Yes. Both are free, need no account and are created in your browser from the numbers on screen. The calculator runs in your browser and nothing is uploaded; you can check the Network tab in DevTools. The PDF library loads from our own site the first time you press PDF.
More tools are on the calculators hub.