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How to Use
- 1Enter the loan principal — the total amount you are borrowing. For a mortgage, this is the home price minus your down payment. For a car loan, it is the vehicle price minus any trade-in value or down payment.
- 2Enter the annual interest rate as a percentage. Current mortgage rates in the US typically range from 6-7% (as of 2024-2025). Auto loan rates range from 5-9% depending on credit score and term. Enter the rate your lender has quoted or use the presets as starting points.
- 3Enter the loan term in years. Common terms are 30 or 15 years for mortgages, 3-7 years for auto loans, and 5-20 years for personal loans. Shorter terms mean higher monthly payments but dramatically less total interest paid.
- 4Optionally, select a preset scenario (30-year mortgage, 5-year car loan, or 0% financing) to auto-populate typical values. These presets serve as quick starting points that you can customize.
- 5Review your results: the monthly payment amount, total interest paid over the life of the loan, the total amount repaid (principal + interest), and a visual breakdown of the principal versus interest share of each payment.
- 6Expand the amortization section to see a year-by-year table showing the principal paid, interest paid, and remaining balance at the end of each year. This reveals how the proportion shifts from interest-heavy early payments to principal-heavy later payments.
About Loan/Mortgage Calculator
The Loan/Mortgage Calculator uses the standard amortization formula employed by banks and financial institutions worldwide: M = P[r(1+r)^n] / [(1+r)^n - 1], where M is the monthly payment, P is the principal (loan amount), r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments (years x 12). For example, a $300,000 mortgage at 6.5% annual interest for 30 years: r = 0.065/12 = 0.005417, n = 360, and M = $300,000[0.005417(1.005417)^360] / [(1.005417)^360 - 1] = $1,896.20 per month.
The amortization schedule reveals one of the most important and often surprising aspects of loan repayment: in the early years, the vast majority of each payment goes toward interest rather than principal. Using the example above, the first monthly payment of $1,896.20 allocates $1,625.00 to interest and only $271.20 to principal. By year 15, the split is roughly even. In the final years, nearly the entire payment reduces the principal. Over the full 30-year term, you pay $382,633 in interest on top of the $300,000 principal — more than doubling the cost of the loan.
This principal-to-interest ratio shift is why financial advisors often recommend making extra principal payments early in a loan's life, when the leverage is greatest. An extra $200/month on the $300,000 mortgage example above would pay off the loan approximately 5 years early and save roughly $72,000 in total interest. The amortization table in this calculator helps you visualize this dynamic and understand the true cost of borrowing over different time horizons.
The choice between a 15-year and 30-year mortgage is one of the most consequential financial decisions homebuyers face. A 15-year term on a $300,000 loan at 6.0% results in a monthly payment of $2,531.57 and total interest of $155,683. The same loan at 30 years (6.5%) costs $1,896.20/month but $382,633 in total interest. The 15-year option saves $226,950 in interest but requires $635 more per month. The 28/36 rule — your mortgage payment should not exceed 28% of gross monthly income, and total debt should not exceed 36% — helps determine which option your budget supports.
The calculator also handles 0% interest scenarios, which are increasingly common in buy-now-pay-later (BNPL) programs, promotional auto financing, and retail installment plans. At 0% interest, the monthly payment is simply the principal divided by the number of payments (P/n). While 0% financing appears free, consumers should be aware that promotional rates often revert to high interest rates if a payment is missed, and the item price may be inflated to compensate for the free financing.
Quick presets for common loan types let you compare scenarios instantly. The mortgage preset loads typical home loan parameters, the car loan preset uses standard auto financing terms, and the 0% financing preset models interest-free installment plans. Adjust any parameter after loading a preset to customize the calculation for your specific situation.
All calculations run entirely in your browser using client-side JavaScript. No loan amounts, interest rates, or financial data are transmitted to any server or stored anywhere. The tool works offline after the page loads, making it suitable for private financial planning, comparing lender offers, and educational use.
Frequently Asked Questions
How is the monthly payment calculated?
The tool uses the standard amortization formula: M = P[r(1+r)^n] / [(1+r)^n - 1], where P is the principal, r is the monthly interest rate (annual rate / 12), and n is the total number of monthly payments. For example, a $200,000 loan at 7% for 30 years: r = 0.00583, n = 360, M = $1,330.60/month. This is the same formula used by banks, mortgage companies, and financial calculators.
What is amortization and why does it matter?
Amortization is the process of gradually paying off a loan through equal monthly payments that cover both principal and interest. Early in the loan, most of each payment goes to interest. Over time, the interest portion shrinks and the principal portion grows. Understanding this schedule is crucial because it reveals the true cost of borrowing and shows why extra payments early in the loan save far more interest than extra payments later.
Does the calculator handle variable or adjustable interest rates?
This calculator assumes a fixed interest rate for the entire loan term. Adjustable-rate mortgages (ARMs) and variable-rate loans change rates periodically (e.g., a 5/1 ARM has a fixed rate for 5 years, then adjusts annually). To model an ARM, you would need to run separate calculations for each rate period. Fixed-rate loans are simpler to plan for, which is why they are the most popular choice for mortgages.
How much mortgage can I afford based on my income?
The widely used 28/36 rule states that your monthly mortgage payment (including principal, interest, taxes, and insurance) should not exceed 28% of your gross monthly income, and your total monthly debt payments should not exceed 36%. For example, with a $6,000/month gross income, your mortgage payment should not exceed $1,680. Enter different principal amounts in the calculator to find a monthly payment within this range.
How does a shorter loan term affect total interest paid?
Shorter terms dramatically reduce total interest. A $300,000 loan at 6.5% over 30 years costs about $382,633 in interest (total: $682,633). The same loan over 15 years at 6.0% costs about $155,683 in interest (total: $455,683) — saving approximately $226,950. The monthly payment is higher ($2,531 vs. $1,896), but you pay off the loan 15 years sooner and save nearly a quarter-million dollars.
What happens if I make extra principal payments?
Extra principal payments directly reduce your outstanding balance, which means less interest accrues in future months. This shortens the loan term and reduces total interest. Even small extra payments add up significantly: an extra $100/month on a $250,000, 30-year mortgage at 6.5% saves approximately $47,000 in interest and pays off the loan about 4 years early. The earlier in the loan you make extra payments, the greater the savings.
Can I calculate a 0% interest loan?
Yes. Enter 0 as the annual interest rate and the calculator divides the principal evenly across all payments. A $12,000 loan over 24 months at 0% equals $500/month with no interest. This is useful for modeling buy-now-pay-later (BNPL) plans, promotional auto financing offers, and interest-free retailer installment programs.
Is my financial data stored or shared?
No. All calculations run entirely in your browser using client-side JavaScript. No loan amounts, interest rates, payment amounts, or any other financial data is transmitted to any server, stored in cookies, or logged by analytics. The tool works offline after the page loads. This makes it suitable for comparing sensitive lender offers, planning home purchases, and private financial modeling.