Guide
Why a 10% Loan Costs 17%
A 10% flat loan over five years is a 17.27% reducing-balance loan. Same headline number, 82% more interest…
Loan Calculator
Works out the monthly payment, total interest and full repayment schedule for any loan from the amount, rate and term.
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In short
Loan Calculator is a free online tool on inputtesthub.com that works out the monthly payment, total interest and full repayment schedule for any loan from the amount, rate and term. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.
How to use the Loan Calculator
- Enter your figures in the input fields.
- The result updates as you type, together with the full working.
- Check the breakdown table to see exactly how the number was reached.
About the Loan Calculator
The Loan Calculator works out the monthly payment, total interest and full repayment schedule for any loan from the amount, rate and term. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.
What people use it for
- Comparing two loan offers before signing.
- Seeing how much a shorter term actually saves in interest.
- Checking what an extra payment each month does to the payoff date.
Details
| Output | Monthly payment, total repaid, total interest, interest as a share of the loan, and a month-by-month amortisation table |
|---|---|
| Extra payments | Applied straight to principal, with the new payoff date and interest saved shown |
The maths behind it
This tool uses the standard amortising loan formula M = P × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1), where P is the principal, r is the monthly rate (annual ÷ 12) and n is the number of months. Every intermediate value is shown on screen, so the result can be checked by hand.
This is the interest maths only. Real loan agreements add arrangement fees, insurance and sometimes early-repayment penalties, so the APR your lender quotes may be higher than the rate you enter here.
Explained in our guides
All guidesFrequently asked questions
Does the Loan Calculator cost anything?
No charge and no sign-up. There is no free tier to run out of because there is no paid tier — inputtesthub.com is funded by advertising rather than by metering the tool.
Is the Loan Calculator safe to use with private information?
No. The Loan Calculator runs entirely in your browser using JavaScript. Because the work happens locally, the tool also keeps working if your connection drops, and closing the tab is all it takes to discard everything.
Can I check the maths myself?
It uses the standard amortising loan formula M = P × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1), where P is the principal, r is the monthly rate (annual ÷ 12) and n is the number of months. The full working is printed under the result, so you can follow every step rather than trusting a black box.
What problem does the Loan Calculator solve?
In practice it gets used for three things: comparing two loan offers before signing. Seeing how much a shorter term actually saves in interest. Checking what an extra payment each month does to the payoff date. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Any caveats I should know about?
This is the interest maths only. Real loan agreements add arrangement fees, insurance and sometimes early-repayment penalties, so the APR your lender quotes may be higher than the rate you enter here.
What are the reference figures here?
Output is Monthly payment, total repaid, total interest, interest as a share of the loan, and a month-by-month amortisation table. Extra payments is Applied straight to principal, with the new payoff date and interest saved shown. These are printed on the page itself, so you do not have to take them on trust.
Is the number rounded?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.
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