Amortization Calculator

Formula

M = P · [r(1 + r)ⁿ] / [(1 + r)ⁿ − 1]

M is the monthly payment; P is the principal loan amount ($200,000); r is the monthly interest rate, calculated as the annual percentage rate divided by 12 (or annual rate ÷ 1,200 for decimals); n is the total number of monthly payments (loan term in years multiplied by 12).

Worked example

Loan amount

200000

Interest rate

6.5

Loan term

30

• Monthly payment: 1,264.14
• Total interest: 255,088.98
• Total of all payments: 455,088.98
• Interest paid in year 1: 12,934.18
• Balance after year 1: 197,764.55
• Number of payments: 360

What an Amortization Calculator Does and Who It Is For

An amortization calculator computes the precise monthly payment required to fully retire a fixed-rate debt over a predetermined term. It also generates an itemized breakdown showing how much of each payment covers interest and how much reduces your principal balance.

This tool is designed for homebuyers evaluating mortgage options, vehicle buyers comparing auto financing lengths, and borrowers looking to refinance existing debt. It helps you see the true cost of borrowing beyond the monthly payment by highlighting total lifetime interest and tracking balance reductions over time.

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Step-by-Step Worked Example

To see how the mathematical formula works in practice, consider a standard fixed-rate home loan with the following inputs:

• Loan amount ($P$): $200,000
• Annual interest rate: 6.5%
• Loan term ($y$): 30 years (360 monthly payments)

1. Calculate Monthly Interest Rate and Payment Count

• Monthly rate ($r$) = $0.065 / 12 \approx 0.00541667$
• Total payments ($n$) = $30 \times 12 = 360$

2. Solve for the Monthly Payment

Using the amortization formula $M = P \cdot [r(1 + r)^n] / [(1 + r)^n - 1]$:

1. $(1 + r)^{360} = (1.00541667)^{360} \approx 6.991798$
2. Numerator: $200,000 \times 0.00541667 \times 6.991798 \approx 7,574.45$
3. Denominator: $6.991798 - 1 = 5.991798$
4. Monthly payment ($M$): $7,574.45 / 5.991798 = \mathbf{$1,264.14}$

3. Analyze the Full Payoff Schedule

Over the full 360-month term, the payments yield the following totals:

• Total of all payments: $360 \times $1,264.14 = \mathbf{$455,088.98}$
• Total interest paid: $$455,088.98 - $200,000 = \mathbf{$255,088.98}$
• Interest paid in year 1: $\mathbf{$12,934.18}$
• Remaining balance after year 1: $\mathbf{$197,764.55}$

Notice that despite paying $$15,169.68$ across 12 monthly installments, the principal decreases by only $$2,235.45$ in the first year. More than 85% of your year-one payments goes directly toward interest.

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How to Interpret the Results

Understanding your amortization figures helps you compare borrowing scenarios with confidence:

Total Interest vs. Principal

In long-term loans (such as 30-year mortgages), total interest often surpasses the original principal balance when rates exceed 6%. In our base example, total interest ($$255,088.98$) is roughly 127% of the original loan balance ($$200,000$). Evaluating this figure helps determine whether a shorter term or an upfront rate buydown is worth considering.

First-Year Equity Growth

Because amortization is front-loaded with interest, equity accumulates slowly during the initial 5 to 7 years. Borrowers planning to sell or relocate within a short window should note that regular monthly payments build very little home equity early on.

Payment Benchmarks Across Loan Sizes

Changing the borrowing amount shifts the monthly payment and total cost proportionally:

• $160,000 loan at 6.5% (30 years): $$1,011.31$ monthly payment
• $200,000 loan at 6.5% (30 years): $$1,264.14$ monthly payment
• $240,000 loan at 6.5% (30 years): $$1,516.96$ monthly payment

Each $$40,000$ change in principal adjusts the monthly cost by approximately $$252.83$ at this interest rate.

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Practical Tips for Managing Your Amortization

• Make targeted principal payments: Paying an extra $$100 to $$200 per month directly toward the principal bypasses compounding interest, shaving years off your term.
• Verify extra-payment policies: Ensure your loan servicer applies additional funds directly to the principal rather than advancing the next scheduled payment.
• Compare 15-year vs. 30-year terms: A 15-year loan features higher monthly payments but drastically lowers your lifetime interest cost and accelerates equity growth from day one.
• Account for full housing expenses: Add property taxes, homeowner insurance, and HOA dues to this baseline principal-and-interest figure to find your complete housing cost (often referred to as PITI).

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When Not to Rely on Basic Amortization

While fixed-rate amortization is standard across banking, this calculator should not be used for:

• Adjustable-Rate Mortgages (ARMs): These loans reset periodically according to market index rates, making lifetime projections variable.
• Interest-Only Loans: During an interest-only period, monthly payments do not reduce the principal balance, and normal amortization formulas do not apply.
• Revolving Credit: Credit cards and home equity lines of credit (HELOCs) use average daily balances and flexible draw periods rather than fixed installment schedules.
• Loans with Balloon Payments: Contracts requiring a lump-sum payoff at a specific maturity date follow different amortization end terms.

Comparison

Scenario	Input	Result
Lower input	Loan amount: 160000	Monthly payment: 1,011.31
Base example	Loan amount: 200000	Monthly payment: 1,264.14
Higher input	Loan amount: 240000	Monthly payment: 1,516.96

Common mistakes

• Confusing APR with the nominal interest rate, which slightly alters the core principal and interest calculation
• Assuming monthly payments decrease over time as the principal balance declines on a fixed-rate loan
• Overlooking escrow costs like homeowner insurance, property taxes, and private mortgage insurance (PMI)
• Failing to account for how heavily interest is front-loaded in the first third of a long amortization schedule
• Rounding payment values prematurely, causing small discrepancies in the final payoff balance

Checklist

• Verify the principal loan balance after subtracting any down payment
• Use the exact annual interest rate, distinguishing between nominal interest rate and APR
• Confirm the loan term in full years (e.g., 15, 20, or 30 years)
• Check whether your loan has an early prepayment penalty before making extra payments
• Remember that basic amortization excludes property taxes, insurance, and HOA fees
• Review year-one interest totals to estimate mortgage interest deductions if itemizing taxes

Calculators Percentage Editorial Team

Calculator guides from the Calculators Percentage team. These introductory examples are educational, not professional advice.

Last reviewed: November 12, 2026

This calculator provides standard amortization schedules for educational and informational purposes only. Actual lender terms, escrow requirements, and loan structures may vary.