Formula
Each Payment: Interest = Balance ร Rate; Principal = Payment - Interest
Interest is calculated on the remaining balance, then subtracted from the fixed payment to determine principal. The principal reduces the balance for the next calculation.
Worked Examples
Example 1: 30-Year Mortgage Amortization
Problem: Create an amortization overview for a $250,000 mortgage at 6% for 30 years.
Solution: Monthly payment calculation:\nP = $250,000, r = 6%/12 = 0.5%, n = 360\n\nM = $250,000 ร [0.005(1.005)^360] / [(1.005)^360 - 1]\nM = $1,498.88/month\n\nPayment #1:\nInterest = $250,000 ร 0.005 = $1,250\nPrincipal = $1,498.88 - $1,250 = $248.88\nNew Balance = $249,751.12\n\nPayment #360:\nInterest = $7.47\nPrincipal = $1,491.41\nFinal Balance = $0
Result: Payment: $1,498.88 | Total Interest: $289,595 over 30 years
Example 2: Impact of Extra Payment on 15-Year Loan
Problem: How does $200 extra monthly affect a $150,000 loan at 5.5% for 15 years?
Solution: Standard payment: $1,225.63/month\nWith $200 extra: $1,425.63/month\n\nWithout extra:\n- 180 payments\n- Total interest: $70,613\n\nWith $200 extra:\n- Paid off in month 144 (12.0 years)\n- Total interest: $55,215\n\nSavings:\n- 36 months earlier (3 years)\n- $15,397 interest saved
Result: $200 extra saves $15,397 and 36 months
Example 3: Year 1 vs Year 30 Payment Breakdown
Problem: Compare principal vs interest in year 1 and year 30 of a $200,000 mortgage at 6.5%.
Solution: Monthly payment: $1,264.14\n\nYear 1 (12 payments):\n- Principal paid: $2,235\n- Interest paid: $12,934\n- Principal %: 14.7%\n\nYear 30 (final 12 payments):\n- Principal paid: $14,649\n- Interest paid: $521\n- Principal %: 96.6%\n\nNote how interest drops from about 85.3% of the first-year cash flow to roughly 3.4% in the final year.
Result: Year 1: 17% principal | Year 30: 98% principal
Frequently Asked Questions
What is an amortization schedule?
An amortization schedule is a table showing each loan payment broken down into principal and interest components, along with the remaining balance after each payment. It demonstrates how the loan balance decreases over time and how the proportion of principal vs. interest changes throughout the loan term.
How does extra payment affect my amortization?
Extra payments go directly to principal, reducing your balance faster than scheduled. This means: 1) Less interest accrues on future payments, 2) More of each subsequent payment goes to principal, 3) You pay off the loan early, 4) You save significantly on total interest. Even small extra payments compound to major savings.
What's the difference between amortization and simple interest?
Simple interest is calculated only on the original principal: Interest = Principal ร Rate ร Time. Amortized loans calculate interest on the remaining balance, which changes with each payment. Credit cards typically use compound interest (interest on interest). Most mortgages and auto loans use amortization.
Can I get a copy of my amortization schedule?
Yes! Your lender must provide one upon request. You can also generate one using calculators like this one. Having a schedule helps you: track your payoff progress, understand your payment breakdown, plan extra payments strategically, and verify your lender's calculations.
How does refinancing affect my amortization?
Refinancing restarts your amortization schedule. If you refinance a 30-year loan after 5 years into a new 30-year loan, you're back to paying mostly interest. However, if the new rate is significantly lower or you refinance to a shorter term, you may still come out ahead. Calculate the total cost of each scenario.
What is negative amortization?
Negative amortization occurs when your payment doesn't cover the interest due, causing the unpaid interest to be added to your principal. Your balance actually grows instead of shrinking. This can happen with certain adjustable-rate mortgages or payment-option loans. It's risky and can lead to owing more than your home is worth.
Background & Theory
The Amortization Calculator - Loan Payment Schedule applies the following established principles and formulas.
A mortgage is a secured loan used to purchase real estate, where the property itself serves as collateral. Understanding how mortgage payments are calculated helps borrowers compare offers, plan budgets, and potentially save hundreds of thousands of dollars over the life of a loan.
The standard monthly mortgage payment for principal and interest is determined by the amortization formula: M = P[r(1+r)^n] / [(1+r)^n - 1], where M is the monthly payment, P is the loan principal (home price minus down payment), r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments (loan term in years times 12). This formula produces level payments over the life of the loan, but the proportion allocated to interest versus principal changes with each payment. In the early years, the majority of each payment covers interest because the outstanding balance is large. As the balance decreases, more of each payment reduces principal. This gradual shift is called amortization.
For example, on a $300,000 loan at 6.5 percent for 30 years, the monthly principal and interest payment is approximately $1,896. In the first month, roughly $1,625 goes to interest and only $271 to principal. By year 15, the split is roughly equal, and in the final year, nearly the entire payment reduces the balance.
The total monthly housing payment typically includes four components, often abbreviated PITI: Principal, Interest, Taxes, and Insurance. Property taxes are assessed annually by local governments, usually ranging from 0.5 to 2.5 percent of assessed value, and are divided into monthly escrow payments collected by the lender. Homeowners insurance protects against damage and liability, and lenders require coverage at least equal to the loan amount.
Private Mortgage Insurance (PMI) is an additional cost required when the down payment is less than 20 percent of the purchase price. PMI protects the lender against default, not the borrower, and typically costs between 0.3 and 1.5 percent of the original loan amount annually. PMI can be removed once the loan-to-value ratio reaches 80 percent through regular payments or appreciation, and is automatically terminated by law at 78 percent LTV.
Fixed-rate mortgages lock the interest rate for the entire loan term, providing predictable payments. The most common terms are 30 years (lower monthly payment, more total interest) and 15 years (higher monthly payment, substantially less total interest). On a $300,000 loan at 6.5 percent, choosing a 15-year term over a 30-year term saves approximately $200,000 in total interest, but requires a monthly payment roughly 50 percent higher.
Adjustable-rate mortgages (ARMs) offer a lower initial rate for a fixed period (commonly 5, 7, or 10 years), after which the rate adjusts periodically based on a market index plus a margin. ARMs carry rate caps that limit how much the rate can increase per adjustment and over the loan's lifetime. ARMs can be advantageous for borrowers who plan to sell or refinance before the adjustment period begins.
Mortgage points are fees paid at closing to reduce the interest rate. One discount point costs 1 percent of the loan amount and typically reduces the rate by approximately 0.25 percent. Points make financial sense when the borrower plans to hold the mortgage long enough for the monthly savings to exceed the upfront cost, usually a break-even period of 4 to 7 years.
Lenders evaluate borrowers using the debt-to-income (DTI) ratio. The front-end ratio compares monthly housing costs to gross monthly income and should generally be below 28 to 31 percent. The back-end ratio includes all monthly debt obligations and should typically remain below 36 to 43 percent. Credit score, employment history, and assets also significantly influence approval and the interest rate offered.
History
The history behind the Amortization Calculator - Loan Payment Schedule traces back through the following developments.
The concept of the mortgage dates to ancient civilizations. In Roman law, the hypotheca allowed a debtor to pledge property as security without surrendering possession. The English word mortgage derives from the Old French mort gage, meaning dead pledge, because the arrangement ended (died) either when the debt was repaid or when the lender foreclosed on the property.
In medieval England, mortgages were typically short-term arrangements requiring a lump-sum repayment. The modern long-term amortizing mortgage did not emerge until the twentieth century. Before the 1930s, American home loans were commonly five-year balloon mortgages requiring renewal or full repayment, which created catastrophic risk for borrowers when the Great Depression caused banks to refuse renewals.
The US federal government transformed mortgage lending during the 1930s. The Federal Home Loan Bank System was created in 1932 to provide liquidity to mortgage lenders. The Federal Housing Administration (FHA), established in 1934, introduced the long-term, fixed-rate, fully amortizing mortgage โ the format that dominates American housing finance today. By insuring lenders against default, the FHA made low-down-payment loans viable and standardized underwriting practices nationwide.
The GI Bill of 1944 (Servicemen's Readjustment Act) provided zero-down-payment VA-guaranteed home loans to returning veterans, fueling the suburban housing boom of the 1950s and 1960s and dramatically expanding homeownership rates. The creation of Fannie Mae (1938) and Freddie Mac (1970) established the secondary mortgage market, allowing lenders to sell mortgages to investors and free up capital for new lending. The first mortgage-backed securities in the 1970s further expanded available capital for home loans.
The Savings and Loan crisis of the 1980s resulted from maturity mismatch โ thrift institutions funded long-term fixed-rate mortgages with short-term deposits โ combined with deregulation and fraud. Approximately 1,000 institutions failed, costing taxpayers an estimated $160 billion. Adjustable-rate mortgages gained popularity partly as a response to this crisis, shifting interest-rate risk from lenders to borrowers.
The 2008 financial crisis was triggered by the collapse of the subprime mortgage market. The originate-to-distribute model incentivized lenders to approve risky loans and sell them into securitization vehicles, leading to widespread defaults when housing prices fell. Millions of foreclosures followed, and the near-collapse of the global financial system prompted the Dodd-Frank Act of 2010, which established qualified mortgage standards, ability-to-repay requirements, and created the Consumer Financial Protection Bureau (CFPB) to oversee mortgage lending practices.
Today, the 30-year fixed-rate mortgage remains uniquely American โ most other countries primarily use adjustable-rate or shorter-term mortgages. Conforming loan limits, set annually by the Federal Housing Finance Agency, determine the maximum loan size eligible for purchase by Fannie Mae and Freddie Mac. In 2024, the limit for most US counties was $766,550, with higher limits in designated high-cost areas.