CodeKitHubWhat Is This Tool?
A loan calculator answers the question every borrower actually has: "what will this cost me per month, and in total?" For a standard fixed-rate amortized loan — which covers most mortgages, car loans and personal loans — the monthly payment follows a standard formula from three inputs: principal, interest rate, and term.
The number that surprises most people isn't the monthly payment — it's the total interest. On a 30-year loan at typical rates, interest can approach or exceed the amount borrowed. Seeing that figure before signing, and comparing it across different terms, is the whole point of running the numbers yourself first. These results are estimates for orientation — your lender's official calculation is what binds.
Why Use It?
- Shows total interest and total cost up front — the figures that matter most for comparing offers.
- Live results as you type — test different rates and terms in seconds.
- Visual principal-vs-interest breakdown so the cost structure is obvious at a glance.
- Term can be entered in years or months, covering everything from a 6-month personal loan to a 30-year mortgage.
- Runs entirely in your browser — loan amounts you type are never transmitted anywhere.
How to Use
- Enter the loan amount (principal).
- Enter the annual interest rate as a percentage (e.g. 6.5).
- Enter the term and choose years or months.
- Read the monthly payment, total interest and total cost — and drag the inputs around to compare scenarios.
Example
Input
Amount: 200,000 · Rate: 6.5% · Term: 30 yearsOutput
Monthly payment: 1,264.14 · Total interest: 255,088.98 · Total paid: 455,088.98Over 30 years at 6.5%, the interest exceeds the original loan — exactly the kind of insight worth having before signing.
Practical tips
- Compare total interest, not monthly payments, when weighing two offers with different terms — a lower monthly payment on a longer term almost always costs more overall.
- Run the same loan at the rate you were quoted and at 0.5% lower: the difference shows what rate-shopping or a better credit score is actually worth on your loan, in real money.
- For mortgages, remember the real monthly outlay adds property tax and insurance on top of this principal-and-interest figure — budget with the full number.
- A useful sanity check before any loan: if the total-interest figure makes you flinch, test how much shortening the term by 5 years changes it.
Where this fits with our other tools
The percentage calculator handles the adjacent quick questions — what 20% down on that amount is, or what percent of your income a payment represents. The date calculator answers "when exactly is this paid off" by adding the term to your start date.
Frequently Asked Questions
How is the monthly payment calculated?
With the standard amortization formula: M = P × r × (1+r)ⁿ ÷ ((1+r)ⁿ − 1), where P is the principal, r the monthly rate (annual ÷ 12), and n the number of months. It's the same math lenders use for fixed-rate loans; differences from a lender's quote usually come from fees, insurance, or rounding conventions.
Why is my lender's quoted payment slightly different?
Real loan offers often add costs this calculator deliberately leaves out: origination fees, mandatory insurance, taxes held in escrow (for mortgages), or a different day-count convention. This tool shows the pure principal-and-interest payment — the right baseline for comparing offers, not the final contract figure.
Does a shorter term always save money?
It always reduces total interest, often dramatically — try 15 vs 30 years on the same amount and watch the total-interest figure. The trade-off is a higher monthly payment. The right choice depends on your monthly budget headroom, which is your call, not a calculator's.
Does this work for mortgages, car loans and personal loans?
Yes — any fixed-rate, regularly amortized loan follows the same math. It does not model variable/adjustable rates, interest-only periods, or balloon payments; for those structures, the lender's own schedule is the only reliable source.
Is the amount I enter sent anywhere?
No. The calculation runs entirely as JavaScript in your browser — nothing is transmitted, stored or logged, so it's safe to try real numbers.
Is this financial advice?
No. It's arithmetic — an estimate for orientation and comparison. Loan decisions involve your full financial situation; for those, consult your lender or a qualified financial advisor, and treat their official figures as the ones that count.