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01Finance & Loans toolCalculated result
Simple Interest Calculator
Interest and total value from principal, rate and time.
100% FreeRuns instantlyNo watermark
- 1Enter detailsAdd the numbers for your scenario.
- 2CalculateVootkit updates the result instantly.
- 3ReviewCheck totals, notes and breakdowns.
Private by designProcessed on your device where possible.
Works on any deviceDesktop, tablet and mobile browsers.
No installationOpen the page and start working.
Always free coreUse the free plan for everyday tasks.
How to use Simple Interest Calculator
Vootkit updates the result instantly.
02Check totals, notes and breakdowns.
03Copy the answer into your workflow.
04Your files stay private
Your work is processed locally in your browser where possible and is never added to a Vootkit upload library.
Learn more about privacySimple interest is the version most people picture when they imagine interest, and the version almost no modern product actually uses. Knowing the difference is worth more than the calculation itself.
What Simple Interest Calculator does
Calculates interest charged or earned on the original principal only, at a flat rate, over a set term — no compounding.
That matters because the gap between simple and compound widens with time. Over one year they are close; over twenty they are not remotely the same number.
Where simple interest actually appears
| Formula | Interest = principal × rate × time |
|---|---|
| Common uses | Short-term personal loans between individuals, some car finance, bond coupons |
| Not used by | Savings accounts, credit cards, mortgages — all compound |
| Over 1 year at 10% | Simple and compound differ by nothing on a single payment |
| Over 20 years at 10% | Simple triples your money; compound multiplies it by about 6.7 |
| Watch for | "Flat rate" car finance, which quotes simple interest on the original balance |
Detailed steps
- Enter the principal — the original amount, not the current balance.
- Enter the annual rate.
- Enter the term in years. Fractions are fine: nine months is 0.75, and eighteen months is 1.5.
- If the product actually compounds, use the compound interest calculator instead — the answer here will be too low.
Worth knowing
Watch for "flat rate" car and personal finance. A flat rate charges interest on the ORIGINAL balance for the whole term, even though you are paying the balance down every month — so a 5% flat rate over four years costs roughly what a 9% reducing-balance rate would. The APR must be disclosed and will reveal it, but the flat rate is the number on the poster, and it is the one people compare.
Frequently Asked Questions
When is interest ever actually simple?
Short-term borrowing where nothing is added back to the balance: a loan between family members, some bond coupon payments, certain car finance agreements. Almost every retail savings and borrowing product compounds, which is why the simple figure usually understates what you will pay and overstates what you will earn.
How much does compounding really change things?
Over short periods, very little. Over long ones, everything. £10,000 at 10% simple interest for twenty years earns £20,000. The same money compounding annually earns about £57,275. The formula difference looks trivial written down and produces nearly three times the result.
My loan says 5% flat rate — is that good?
It is worse than it sounds. A flat rate is charged on the original amount for the full term while your actual balance falls every month, so the effective rate is close to double. Ask for the APR, which is required to reflect the reducing balance, and compare that instead.
Can I use this for a savings account?
You can, but it will understate what you earn, because savings accounts pay interest on interest. Use the compound interest calculator for anything where the interest stays in the account — the simple figure is only correct if you withdraw every payment as it arrives.
Is Simple Interest Calculator free?
Yes. The Vootkit free plan includes 5 tool runs a day. Upgrade to Vootkit Pro for unlimited daily use, an ad-free workspace and saved workflows.
Are my files uploaded?
No. Simple Interest Calculator runs entirely in your browser — your file is processed on your own device and never sent to a server. There is nothing for us to store or delete.
Do I need to install anything?
No. Simple Interest Calculator works in any modern browser on desktop, tablet or phone. Open the page and start.
How often can I use it? Is there a daily limit?
On the free plan you get 5 tool runs a day. When you reach the limit you'll see a prompt to upgrade, and it resets the next day. Vootkit Pro removes the cap entirely for unlimited daily use.
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This tool processes everything locally in your browser. You can disconnect from the internet after the page loads and it will still work.