Loan Calculator
Loan Calculator
The Loan Calculator is a versatile financial tool designed to help you compute the periodic payment required to fully amortize a fixed-rate loan. Whether you are evaluating a personal loan, a student loan, a business loan, or any other type of installment loan, this calculator provides the key information you need to understand the true cost of borrowing and make informed financial decisions.
Understanding how loans work is essential for making sound financial choices. When you take out a loan, you borrow money that must be repaid over time with interest. The periodic payment includes both a portion toward reducing the principal balance and a portion covering interest accrued since your last payment. Over time, the proportion going toward principal increases as the outstanding balance decreases through a process called amortization.
One of the most important features of this calculator is the ability to model extra payments. By making additional principal payments above the required periodic payment, you can pay off your loan faster and save thousands of dollars in interest [cfpb]. The analysis shows exactly how much you can save and how much sooner you can become debt-free, helping you decide whether making extra payments fits your budget.
The standard loan amortization formula is based on the time value of money principles that govern all fixed-rate installment loans. The same formula is used by banks and financial institutions for mortgages, auto loans, personal loans, and most other installment lending products [federal-reserve]. Understanding this formula helps you see why longer terms reduce monthly payments but dramatically increase total interest.
For more information, see the Personal Loan Calculator.
For more information, see the Business Loan Calculator.
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Enter the Loan Principal: The total amount you plan to borrow. For a mortgage, this is the purchase price minus your down payment. For an auto loan, it is the vehicle price minus any trade-in value and down payment.
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Enter the Annual Interest Rate: Enter the APR as a percentage. If you have multiple loan offers, compare their APRs rather than just the interest rate, as APR includes fees.
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Enter the Loan Term: Enter the loan duration in years. Common terms include 15 or 30 years for mortgages, 3 to 7 years for auto loans, and 1 to 5 years for personal loans.
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Select Payment Frequency: Monthly payments are most common, but you can also choose weekly, biweekly, or quarterly schedules. The payment frequency affects both the payment amount and total interest.
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Optionally Enter Extra Payments: Enter any additional amount you plan to pay above the required payment each period. Even small extra payments can significantly reduce total interest and shorten the loan term.
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Review Your Results: Press Calculate to see your periodic payment, total interest over the full loan term, total cost, and the percentage of total payments that go toward interest. If you entered extra payments, the calculator shows the interest saved and the new payoff date.
Example Calculation
A 300,000 dollar mortgage at 6.5 percent for 30 years with monthly payments:
- Monthly payment: approximately 1,896 dollars
- Total interest: approximately 382,000 dollars
- Total cost of the loan: 682,000 dollars
- Percentage of payments going to interest: 56 percent
With extra payments: Adding 100 dollars extra each month saves approximately 47,000 dollars in interest and pays off the loan 6 years early.
For more information, see the Auto Loan Calculator.
The periodic payment is calculated using the standard amortization formula:
Where P is the principal, i is the periodic interest rate (annual rate divided by the number of payments per year), and N is the total number of payments over the loan term.
The remaining balance after k payments can be calculated:
Total interest over the life of the loan:
For a 300,000 dollar loan at 6.5 percent over 30 years, total interest is approximately 382,000 dollars. This means more than half of your total payments go toward interest rather than principal, illustrating why understanding the total cost of borrowing is essential.
Monthly payments and total interest for different loan amounts and rates on a 30-year fixed-rate mortgage:
| Loan Amount | 5.0% | 6.0% | 6.5% | 7.0% | 8.0% |
|---|---|---|---|---|---|
| 200,000 | 1,074 (186,512) | 1,199 (231,677) | 1,264 (255,129) | 1,330 (279,018) | 1,467 (328,287) |
| 300,000 | 1,610 (279,767) | 1,799 (347,516) | 1,896 (382,693) | 1,996 (418,527) | 2,201 (492,430) |
| 400,000 | 2,147 (373,023) | 2,398 (463,354) | 2,528 (510,258) | 2,661 (558,036) | 2,935 (656,574) |
| 500,000 | 2,684 (466,279) | 2,998 (579,193) | 3,161 (637,822) | 3,326 (697,545) | 3,669 (820,716) |
Extra payments on a 300,000 dollar loan at 6.5 percent:
| Extra Payment | Interest Saved | Payoff Reduced By |
|---|---|---|
| 50/month | 27,000 | 3.5 years |
| 100/month | 47,000 | 6.0 years |
| 200/month | 90,000 | 7.0 years |
| 500/month | 185,000 | 14.0 years |
An amortization schedule shows every payment over the life of a loan, breaking down how much goes to principal and how much to interest. Understanding this schedule helps you see exactly how your loan works and plan strategies to minimize interest costs.
In the early years of a 30-year mortgage, the vast majority of each payment goes toward interest. For a 300,000 dollar loan at 6.5 percent, the very first payment of 1,896 dollars consists of approximately 1,625 dollars in interest and only 271 dollars in principal reduction. This means you build equity very slowly at first. After 10 years of payments totaling 227,520 dollars, you would have reduced the principal by only about 39,000 dollars — the rest went to interest.
By year 20 of the same loan, each payment is roughly evenly split between principal and interest. In the final years, most of each payment goes to principal, rapidly accelerating equity building. The final payment on a 30-year mortgage consists almost entirely of principal with just a few dollars of interest.
This front-loaded interest structure is why making extra payments early in the loan term is so effective. An extra 100 dollars in the first year saves more interest than the same 100 dollars in year 20 because it avoids the highest-interest years of the loan. If you can afford extra payments only for a limited period, making them in the first few years maximizes their impact.
Making extra payments toward principal is one of the most effective ways to save on interest. Even small additional payments made consistently can reduce total interest by tens of thousands of dollars over the life of a loan. When making extra payments, specify that the additional amount should be applied to principal, not treated as an early payment of next month's bill.
Consider biweekly payment schedules for mortgages. Making half a monthly payment every two weeks results in 13 full payments per year instead of 12, directly accelerating principal reduction. Many lenders offer automatic biweekly payment programs. On a 300,000 dollar loan at 6.5 percent, switching to biweekly payments saves approximately 65,000 dollars in interest.
Refinancing makes sense when rates drop significantly below your current rate. A general rule is to refinance if you can reduce your rate by at least 1 percent and plan to stay in the home for at least 3 to 5 years to recover the closing costs.
Different types of loans serve different purposes and have distinct characteristics that affect your payment and total cost:
Mortgages: Secured by real estate, mortgages offer the lowest interest rates of any consumer loan because the lender has collateral. Terms range from 15 to 30 years for fixed-rate loans. The mortgage interest deduction may reduce the after-tax cost for homeowners who itemize deductions [investopedia].
Auto Loans: Secured by the vehicle, auto loans have moderate interest rates and terms of 3 to 7 years. Because vehicles depreciate rapidly, it is possible to owe more than the car is worth in the early years, known as being upside down on the loan.
Personal Loans: Unsecured loans with higher interest rates reflecting the lack of collateral. Terms typically range from 1 to 5 years. Personal loans are often used for debt consolidation, home improvements, or major purchases. Interest rates depend heavily on credit score.
Student Loans: Federal student loans offer fixed rates, income-driven repayment options, and forgiveness programs that are not available from private lenders. Private student loans typically have variable or fixed rates based on credit. Federal loans should be exhausted before considering private loans.
For more information, see the Debt Consolidation Calculator.
This calculator assumes a fixed interest rate and level payments for the entire loan term. Adjustable-rate loans require recalculation after each rate change and cannot be accurately modeled with this formula. The calculator does not account for origination fees, closing costs, PMI, property taxes, or insurance, which add to the true cost of borrowing.
Extra payments may be subject to prepayment penalties on some loans, particularly personal loans and auto loans. Always check your loan agreement before making extra payments. The calculator assumes consistent extra payments from the start of the loan; irregular extra payments will have a different impact.
- How is my monthly payment calculated?
- Using the amortization formula: M = P times r times (1+r)^n divided by ((1+r)^n - 1), where P is principal, r is the monthly rate, and n is the total number of payments.
- What is an amortization schedule?
- It breaks down every payment showing how much goes to interest versus principal. Early payments are mostly interest. Over time, more goes toward principal.
- Does making extra payments reduce total interest?
- Yes. Extra payments go directly to principal, reducing the balance faster. This can save thousands of dollars and shorten the loan term significantly.
- What is the difference between APR and interest rate?
- The interest rate is the cost of borrowing the principal. APR includes the rate plus fees expressed as a yearly rate, giving a more complete picture.
- How does loan term length affect total cost?
- A shorter term means higher monthly payments but much less total interest. A longer term means lower payments but significantly more interest over the life of the loan.
- [1]Consumer Financial Protection Bureau. (n.d.). What Is an Amortization Schedule?
- [2]Federal Reserve. (n.d.). Consumer Handbook on Adjustable-Rate Mortgages.
- [3]Investopedia. (n.d.). Amortization Schedule Definition.
- [4]Bankrate. (n.d.). Amortization Calculator.
- [5]NerdWallet. (n.d.). Loan Calculator.
- [6]U.S. Department of Education. (n.d.). Student Loan Repayment.
Last updated: July 10, 2026
UnByte — Independent Software Engineering
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