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Amortization Calculator: Full Payment Schedule with Principal & Interest Breakdown

Generate a complete month-by-month amortization schedule showing exactly how each payment splits between principal and interest. See your remaining balance after every single payment, understand why early payments are mostly interest, and plan extra payments strategically. All calculations run locally. Your financial data never leaves your browser.

Amortization Calculator

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About Amortization Calculator

An amortization calculator helps you understand how a loan is paid off over time. It shows how each monthly payment is divided between principal and interest, and displays the remaining balance after each payment.

Features:

  • Calculate monthly payment amount
  • View detailed amortization schedule
  • See principal vs interest breakdown
  • Understand remaining balance over time
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How Amortization Actually Works

Amortization is the process of paying off a loan through equal periodic payments that cover both principal and interest. The word comes from the Latin "admortire" (to kill). You're slowly killing the debt.

Here's what surprises most borrowers: on a 30-year $300,000 mortgage at 6.5%, your monthly payment is $1,896. But in month 1, only $271 goes to principal. The other $1,625 is pure interest. That's 85.7% interest. By month 180 (halfway through), the split is roughly 50/50. By the final year, almost everything goes to principal.

The math behind this: interest each month = remaining balance × (annual rate / 12). Since the balance is highest at the start, interest charges are highest at the start. Your fixed payment minus that month's interest = principal reduction. As the balance drops, interest drops, so more of the same payment goes to principal. It's a self-accelerating process.

The standard amortization formula for monthly payment is: M = P × [r(1+r)ⁿ] / [(1+r)ⁿ − 1], where P = principal, r = monthly rate (annual ÷ 12), n = total payments. This formula was derived in the 17th century and hasn't changed since. Every bank in the world uses it.

One thing the formula doesn't tell you: total interest paid. On that $300,000 / 30-year / 6.5% loan, you'll pay $382,633 in total interest, more than the original loan amount. That's why even small rate differences matter enormously over 30 years. A 0.25% rate reduction on this loan saves $16,000+ in interest.

How to Use

  1. 1Enter the total loan amount (principal only, not including interest).
  2. 2Enter the loan term: years and months (e.g., 30 years 0 months for a standard mortgage).
  3. 3Enter the annual interest rate (nominal rate, not APR).
  4. 4Click Calculate to generate the full month-by-month schedule.
  5. 5Scroll through the table to see principal/interest split for any specific month.

When You Need an Amortization Schedule

Planning extra payments strategically

An amortization schedule shows you exactly where each dollar goes. If you can make an extra $500 payment in month 12, you can see it eliminates months 348-360 of interest. Early extra payments have dramatically more impact than late ones because they reduce the balance that future interest is calculated on.

Comparing loan offers side by side

Two lenders offer you 6.25% for 30 years vs 5.875% for 15 years. The monthly payments are very different, but which costs less total? Generate both schedules and compare total interest paid. Often the 15-year loan saves $100K+ in interest despite higher monthly payments.

Tax deduction planning (US mortgage interest)

In the US, mortgage interest is tax-deductible (up to $750K loan amount). The amortization schedule tells you exactly how much interest you'll pay each calendar year, which is useful for estimating your Schedule A deduction. Year 1 interest is much higher than year 25 interest.

Refinance break-even analysis

You're 8 years into a 30-year mortgage and considering refinancing. The schedule shows your current remaining balance and how much interest you'd pay continuing vs starting a new loan. Factor in closing costs (typically 2-5% of loan amount) to find the break-even month.

Things Most People Get Wrong

1

Use the NOMINAL rate, not APR

APR includes fees and closing costs spread over the loan life. The amortization formula needs the nominal interest rate (the one on your loan agreement). If your APR is 6.8% but your nominal rate is 6.5%, use 6.5%. APR is for comparing loan offers; nominal rate is for calculating actual payments.

2

This schedule assumes no extra payments

The standard amortization schedule shows minimum required payments only. If you make extra payments, the actual payoff will be faster and total interest will be lower. Use our Mortgage Payoff Calculator to model extra payment scenarios specifically.

3

Adjustable-rate mortgages (ARMs) break this schedule

This calculator assumes a fixed rate for the entire term. If you have a 5/1 ARM, the schedule is only accurate for the first 5 years. After the rate adjusts, you'd need to recalculate with the new rate and remaining balance. Fixed-rate loans are the only ones with a truly predictable schedule.

4

Real monthly cost is higher than the payment shown

The amortization payment covers only principal + interest (P&I). Your actual monthly housing cost includes property tax (~1-2% of home value/year), homeowner's insurance (~$1,200-2,400/year), and possibly PMI (0.5-1% of loan/year if down payment < 20%). Budget for P&I + T&I together.

Real Amortization Scenarios

Standard 30-year mortgage: first vs last payment

$350,000 loan at 6.75% for 30 years (360 payments).

Input

Principal: $350,000 | Rate: 6.75% | Term: 30 years

Output

Monthly payment: $2,270.56. Payment #1: $1,968.75 interest + $301.81 principal (86.7% interest). Payment #360: $14.63 interest + $2,255.93 principal (0.6% interest). Total interest over 30 years: $467,401, which is 133% of the original loan.

5-year auto loan: faster principal paydown

$28,000 car loan at 5.9% for 5 years (60 payments).

Input

Principal: $28,000 | Rate: 5.9% | Term: 5 years

Output

Monthly payment: $540.89. Payment #1: $137.67 interest + $403.22 principal (25.5% interest). By month 30 (halfway): $74.12 interest + $466.77 principal. Total interest: $4,453. Shorter terms mean much less interest dominance in early payments.

Limitations

  • Generates a standard amortization schedule with equal monthly payments. Does not support balloon payments or interest-only periods.
  • Rounding in monthly payment calculations may cause the final payment to differ slightly from the regular amount.
  • Does not include escrow items (taxes, insurance) in the payment schedule. These are typically separate.
  • Maximum loan term supported is 50 years. Very long-term calculations may have small rounding accumulation.

Features

  • Complete month-by-month schedule for any loan term
  • Principal vs interest breakdown with visual progress bars
  • Running balance column showing remaining debt after each payment
  • Summary: monthly payment, total paid, total interest
  • Supports any loan amount from $1,000 to $10,000,000+
  • Custom terms: years + months for non-standard loan lengths
  • Your financial data stays private. All calculations run locally in the browser

Frequently Asked Questions

Why is 85% of my first payment going to interest?

Because interest is calculated on the remaining balance, and at the start, the balance is the full loan amount. On a $300K loan at 6.5%, month 1 interest = $300,000 × 6.5% ÷ 12 = $1,625. Your payment is $1,896, so only $271 reduces the principal. This ratio improves every month as the balance drops. By year 15, it's roughly 50/50.

How much total interest will I pay on a 30-year mortgage?

Typically 80-150% of the original loan amount, depending on the rate. At 6%: ~$347K interest on a $300K loan (116%). At 7%: ~$418K (139%). At 4%: ~$215K (72%). This is why rate shopping matters. Even 0.25% less can save $15,000-20,000 over 30 years. The 15-year option roughly halves total interest.

What's the difference between this and a loan calculator?

A loan calculator gives you the monthly payment amount. An amortization calculator gives you the full schedule: every single payment broken down into principal and interest, with the running balance. Use the loan calculator for quick "can I afford this?" checks. Use this for detailed planning, tax estimates, and extra payment strategy.

Does this work for car loans and student loans too?

Yes, any fixed-rate, fully-amortizing loan. Car loans (typically 3-7 years), personal loans (2-5 years), student loans (10-25 years), and mortgages (15-30 years) all use the same amortization formula. The only loans this doesn't apply to are interest-only loans, balloon loans, or variable-rate loans after the rate changes.

Should I get a 15-year or 30-year mortgage?

Math says 15-year wins: on a $300K loan at 6%, you pay $155K less in total interest. But the monthly payment is $2,532 vs $1,799, that's $733/month more. If that extra $733 would go to investments earning >6% after tax, the 30-year might be better financially. If you'd just spend it, take the 15-year. Run both schedules here and compare.

Are these amortization numbers reliable for loan planning?

Yes. The schedule uses the standard amortization formula (M = P[r(1+r)^n]/[(1+r)^n-1]) and is mathematically exact for fixed-rate, fully amortizing loans. Every row shows the precise principal/interest split for each payment. Note: this does not account for fees, taxes, insurance, or rate changes on variable loans. For official loan terms, refer to your lender's disclosure documents. This tool is for planning purposes, not financial advice.

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All calculations happen entirely in your browser. No financial data is uploaded to any server. Your loan details never leave your device.

In-Depth Guide

How to Read Amortization Schedule: A Clear Guide

A plain-English guide to reading amortization schedules: what each column means, why the interest-to-principal ratio shifts, and how to save money.

Read guide

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