What This Calculator Does
You signed a mortgage. The monthly payment fits your budget. But where does that money actually go? In the first year, most of it disappears into interest. An amortization calculator shows you exactly how each payment splits between principal and interest, from the first month to the last.
This calculator works for any fixed-rate loan, including mortgages, auto loans, and personal loans. Understanding your amortization schedule helps you plan extra payments, evaluate refinancing options, and see the true cost of borrowing over time.
The numbers can be sobering. According to a June 2026 report, a buyer financing the median-priced U.S. home ($403,200) with 20% down at the current 30-year fixed rate of 6.49% will pay $413,700 in interest over the life of the loan. That is more than the home itself costs. Freddie Mac's Primary Mortgage Market Survey tracks weekly mortgage rate averages and is the standard source for current rate data.
Inputs Required
- Loan Amount: The original amount borrowed (home price minus down payment)
- Interest Rate: The annual interest rate on the loan
- Loan Term: The repayment period in years
Outputs Provided
- Monthly Payment: Your fixed payment amount each month
- Principal Paid: The portion reducing your loan balance
- Interest Paid: The cost of borrowing for that period
- Remaining Balance: What you still owe after each payment
- Full Schedule: Month by month breakdown for the entire loan term
How the Calculation Works
Amortization uses a fixed monthly payment formula. Each month, interest is calculated on the remaining balance. The rest of the payment goes toward reducing the principal. Because the balance decreases over time, interest charges fall while principal payments rise.
M = P x [r(1+r)^n] / [(1+r)^n - 1]
- M is the monthly payment
- P is the principal (loan amount)
- r is the monthly interest rate (annual rate divided by 12)
- n is the total number of monthly payments
For each month: Interest = Remaining Balance x Monthly Rate. Principal = Monthly Payment minus Interest. New Balance = Previous Balance minus Principal Paid. This cycle repeats for every month of the loan term.
How to Use the Calculator
- Enter your loan amount (for a mortgage, this is the home price minus your down payment)
- Input the annual interest rate (check your loan estimate or use Freddie Mac's current rate)
- Select the loan term in years (15, 20, or 30 are most common)
- View the monthly payment summary at the top
- Switch between the chart view and table view to explore the full schedule
If you are comparing a 15-year versus a 30-year mortgage, run both scenarios. A 15-year loan at the current 5.79% rate saves roughly $250,000 in lifetime interest compared to a 30-year at 6.49% on the same loan amount, though the monthly payment is higher. You can also use our Mortgage Calculator for a broader payment estimate including taxes and insurance.
Example Calculations
Example 1: The Median Home in 2026
Consider a $322,560 loan (the median U.S. home price of $403,200 with 20% down) at 6.49% interest for 30 years:
- Monthly payment: $2,045
- Month 1 interest: $1,743.90, principal: $301.10
- Month 360 interest: $11.03, principal: $2,033.97
- Total interest paid: $413,700 (more than the loan itself)
- Total paid over 30 years: $736,260
In the first month, only about 15% of the payment goes toward principal. By the final year, nearly 99% does. This is the nature of amortization. The interest portion is highest when the balance is largest, which is at the start.
Example 2: The 15-Year Comparison
The same $322,560 loan at 5.79% for 15 years:
- Monthly payment: $2,690 (about $645 more per month)
- Total interest paid: $161,322
- Interest savings vs. 30-year: approximately $252,000
The monthly payment is higher, but you pay less than half the total interest. For borrowers who can afford the higher payment, a 15-year loan is one of the most effective ways to build equity quickly. Use our Mortgage Payoff Calculator to model additional principal payments on a 30-year loan as an alternative.
Real World Scenarios
Planning Extra Payments
David has a 30-year mortgage on a $280,000 loan at 6.5% but wants to pay it off in 20 years. By reviewing the amortization table, he can see exactly how much principal he needs to add to each payment to hit that goal. One extra payment per year on a 30-year loan can cut roughly 5 to 6 years off the term and save tens of thousands in interest. The Consumer Financial Protection Bureau offers guidance on amortization for homeowners.
Comparing Loan Options with Different Rates
Maria is choosing between two loan offers: one at 6.25% with $3,000 in closing costs and another at 6.49% with no closing costs. Running both through the amortization calculator shows the total interest for each over 30 years. The lower rate saves about $16,000 in interest over the life of the loan, but it takes roughly 4 years to break even on the closing costs. If Maria plans to sell within 5 years, the no-cost loan is the better choice. For a deeper comparison, try our Refinance Calculator.
Tax Planning and Deductible Interest
Homeowners who itemize deductions can use the amortization schedule to identify the exact interest paid during a tax year, which may be deductible on Schedule A. The table makes it simple to sum interest payments for any given calendar year. In the early years of a mortgage, the deductible interest is much higher than in later years, which affects the tax benefit of homeownership.
Why This Calculation Matters
Most borrowers focus on the monthly payment. That number looks manageable. But the total cost tells a different story. At current 2026 rates, a 30-year mortgage on the median U.S. home costs more in interest than the home itself. Each percentage point of interest is worth roughly $65,000 to $80,000 over the life of a 30-year loan on a median-priced home.
An amortization schedule reveals the full picture: how long it takes to own more than half of your home, how much interest you pay in total, and how extra payments dramatically reduce that amount. It transforms an abstract debt into a clear, actionable repayment plan.
Common Mistakes to Avoid
- Assuming all payments are the same split: Early payments are mostly interest. On a 30-year loan at 6.49%, the first payment is about 85% interest. This changes significantly over the loan term.
- Ignoring the total interest: The monthly payment looks manageable, but the total interest can exceed the original loan amount. At current rates, a $322,560 loan generates $413,700 in interest over 30 years.
- Not accounting for extra payments: Even one extra payment per year can cut years off your loan. Always confirm there is no prepayment penalty with your lender first.
- Confusing APR with interest rate: Use the stated interest rate, not the APR, for amortization calculations. APR includes fees and costs that are not part of the monthly interest calculation.
- Forgetting about property taxes and insurance: This calculator shows principal and interest only. Your actual monthly payment to the lender (PITI) also includes property taxes and homeowners insurance, often held in an escrow account.
Limitations of This Calculator
This tool generates a standard amortization schedule for fixed-rate loans. It does not handle adjustable-rate mortgages (ARMs), interest-only loans, or balloon payments. The schedule assumes you make exactly the scheduled payment every month with no extra payments. Real-world loans may include escrow payments for taxes and insurance, which are separate from the amortized principal and interest. For variable-rate loans, the schedule changes every time the rate adjusts. This calculator does not replace professional financial advice from a lender or mortgage broker.
Authoritative Research and Resources
- Freddie Mac Primary Mortgage Market Survey - The standard weekly benchmark for U.S. mortgage rates, updated every Thursday. Use this to find the current average rate for your amortization calculation.
- Consumer Financial Protection Bureau: What Is Amortization? - A plain-English government resource explaining amortization schedules and why they matter for homeowners.
- Investopedia: Typical Mortgage Debt in 2026 - Current data on average mortgage balances, monthly payments, and generational debt trends as of 2026.
For related calculations, try our Mortgage Calculator, Mortgage Payoff Calculator, or Refinance Calculator.