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Amortization Calculator

Build a full month-by-month amortization schedule for any fixed-rate loan. Switch between monthly and yearly views.

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Monthly payment

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Total interest

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Amortization schedule

Year Payment Principal Interest Balance

For general information only, not financial advice. Results are estimates — your actual loan, mortgage or return will depend on the lender, your credit, fees and other terms. Talk to a qualified professional before making decisions.

What an amortization calculator does

The amortization calculator turns a loan amount, interest rate and term into the exact monthly payment, then builds the full amortization schedule — every payment number, the split between principal and interest, and the remaining balance after each one. Switch between a monthly view (every single payment) and a yearly summary (twelve months collapsed into a row) depending on whether you want the panorama or the detail.

The formula every lender uses

M = P × [r(1+r)n] ÷ [(1+r)n − 1]

where P is the loan amount, r is the monthly interest rate (APR ÷ 12 ÷ 100) and n is the total number of monthly payments (years × 12). The same payment goes out every month, but the split changes — early on you pay mostly interest because the balance is huge; by the end you pay mostly principal because the balance is small.

How to read a schedule

Look at month 1 of a 30-year $200,000 mortgage at 6.5%: roughly $1,083 of the $1,264 payment is interest, and only about $181 reduces the principal. Move to month 360 and that flips — almost the entire payment is principal, with just a few cents of interest left. Somewhere in between, the principal column overtakes the interest column. On a 30-year 6.5% loan that crossover happens around year 19; on a 5-year 8% auto loan it happens around month 24. The yearly summary makes that turning point easy to spot.

Where amortization shows up in real life

  • Mortgages. The biggest amortizing loan most people ever have.
  • Auto loans. Typically 36–72 months on a standard amortization schedule.
  • Personal and student loans. Same math, different terms.
  • Small business term loans. Often 5–10 years amortized.

Revolving credit (credit cards) and interest-only mortgages do not amortize. For credit-card payoff math, the credit card payoff calculator uses the right model.

Strategies that change the curve

The schedule above assumes you pay the regular amount every month. Two changes can dramatically reduce total interest: shorter terms (a 15-year mortgage often saves $100,000+ vs. 30-year on the same loan), and extra principal payments (even an extra $100/month on a 30-year mortgage can shave 4–5 years off the loan). Both are worth running through the mortgage calculator or loan calculator for the side-by-side numbers.

Frequently asked questions

What is loan amortization?

Amortization is the process of paying off a loan with equal periodic payments. Each payment covers all the interest accrued for that period plus some principal, so the balance shrinks until it hits zero on the final payment.

Why is early-loan interest so high?

Because interest is calculated on the remaining balance. At the start of a 30-year mortgage, the balance is huge, so most of your payment is interest. As principal drops, the interest portion shrinks and the principal portion grows — the classic amortization curve.

When does my loan flip to mostly principal?

It depends on the rate and term. A 30-year mortgage at 6.75% flips around year 18–20. A 5-year auto loan at 8% flips around month 24. Use the schedule above and look for the row where the principal column first exceeds the interest column.

How do extra payments change the schedule?

An extra principal payment shrinks the balance immediately, so every subsequent month's interest is smaller — which means more of each future payment goes to principal. The loan ends earlier and total interest drops, sometimes by a lot.

Does this calculator handle 0% interest?

Yes. At 0%, the monthly payment is simply principal divided by the number of months, and every dollar of every payment goes to principal — no interest column to speak of.

What is the amortization formula?

Monthly payment M = P × [r(1+r)^n] ÷ [(1+r)^n − 1], where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12), and n is the number of months. Each month, interest = remaining balance × r, principal = M − interest.

Worked example

A $200,000 loan at 6.5% over 30 years.

  • Monthly rate: 6.5 ÷ 12 ÷ 100 = 0.5417% · 360 payments
  • Monthly payment: $1,264.14
  • Month 1: interest = 200,000 × 0.005417 ≈ $1,083.33 · principal ≈ $180.81 · balance ≈ $199,819.19
  • Month 180 (year 15): about half the balance gone, balance ≈ $142,000
  • Final month 360: balance closes to $0.00
  • Total of payments: 1,264.14 × 360 = ~$455,089 · Total interest: ~$255,089

Total interest is more than the original loan amount — a normal result for a 30-year term. Cut the term to 15 years and total interest drops to about $113,000.

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