Amortization Calculator — Full Payment Schedule
| Month | Payment | Principal | Interest | Balance |
|---|---|---|---|---|
| 1 | $400.76 | $275.76 | $125.00 | $19,724.24 |
| 2 | $400.76 | $277.48 | $123.28 | $19,446.76 |
| 3 | $400.76 | $279.22 | $121.54 | $19,167.54 |
| 4 | $400.76 | $280.96 | $119.80 | $18,886.58 |
| 5 | $400.76 | $282.72 | $118.04 | $18,603.86 |
| 6 | $400.76 | $284.48 | $116.27 | $18,319.38 |
| 7 | $400.76 | $286.26 | $114.50 | $18,033.11 |
| 8 | $400.76 | $288.05 | $112.71 | $17,745.06 |
| 9 | $400.76 | $289.85 | $110.91 | $17,455.21 |
| 10 | $400.76 | $291.66 | $109.10 | $17,163.55 |
| 11 | $400.76 | $293.49 | $107.27 | $16,870.06 |
| 12 | $400.76 | $295.32 | $105.44 | $16,574.74 |
| 13 | $400.76 | $297.17 | $103.59 | $16,277.57 |
| 14 | $400.76 | $299.02 | $101.73 | $15,978.55 |
| 15 | $400.76 | $300.89 | $99.87 | $15,677.65 |
| 16 | $400.76 | $302.77 | $97.99 | $15,374.88 |
| 17 | $400.76 | $304.67 | $96.09 | $15,070.21 |
| 18 | $400.76 | $306.57 | $94.19 | $14,763.64 |
| 19 | $400.76 | $308.49 | $92.27 | $14,455.16 |
| 20 | $400.76 | $310.41 | $90.34 | $14,144.74 |
| 21 | $400.76 | $312.35 | $88.40 | $13,832.39 |
| 22 | $400.76 | $314.31 | $86.45 | $13,518.08 |
| 23 | $400.76 | $316.27 | $84.49 | $13,201.81 |
| 24 | $400.76 | $318.25 | $82.51 | $12,883.56 |
What Is an Amortization Schedule?
An amortization schedule breaks every loan payment into two components: the portion that pays interest and the portion that reduces the principal. For any fixed-rate installment loan — personal loan, auto loan, student loan, or mortgage — the monthly payment stays constant, but the split between interest and principal shifts with each payment. Early payments are mostly interest; later payments are mostly principal.
The word "amortize" comes from the Old French amortir, meaning to kill off. An amortization schedule is literally a plan for killing off a debt over time through scheduled payments.
The Amortization Formula
The standard amortizing payment formula is:
M = P × [r(1+r)n] / [(1+r)n − 1]
| Variable | Meaning | Example ($20,000 at 7.5% for 5 yrs) |
|---|---|---|
| M | Monthly payment | $400.76 |
| P | Principal (loan amount) | $20,000 |
| r | Monthly interest rate (annual ÷ 12) | 7.5% ÷ 12 = 0.625% = 0.00625 |
| n | Total number of monthly payments | 5 × 12 = 60 |
Step-by-Step Worked Example
Loan: $20,000, Rate: 7.5%, Term: 5 years (60 months)
How Extra Payments Save Money
Any additional payment applied to principal reduces the balance immediately. Because interest is calculated as balance × monthly rate, a lower balance means less interest every single subsequent month. Extra payments effectively shorten the loan term and reduce total interest in a non-linear way — the earlier you make them, the larger the savings.
| Extra Payment/Mo | Months to Payoff | Total Interest | Interest Saved | Months Saved |
|---|---|---|---|---|
| $0 (standard) | 60 | $4,046 | — | — |
| $50 | 53 | $3,624 | $422 | 7 |
| $100 | 48 | $3,269 | $777 | 12 |
| $200 | 40 | $2,710 | $1,336 | 20 |
| $500 | 27 | $1,853 | $2,193 | 33 |
An extra $100/month on a $20,000 5-year loan saves 12 payments and $777 in interest. That $100 monthly commitment yields a risk-free 7.5% return on every dollar — better than most savings accounts. The "return" is guaranteed because interest savings are certain, unlike investment returns.
Amortization Schedule Over the Loan Life
The interest-to-principal ratio shifts dramatically over a loan's life. For a $20,000 loan at 7.5% for 5 years, the first payment is 31.2% interest and 68.8% principal. By payment 30 (halfway), it shifts to 18.7% interest and 81.3% principal. By the final payment, 99.4% is principal. This is why paying off a loan in year 1 or 2 saves far more interest than paying extra in year 4 or 5.
| Period | Approx. Interest Portion | Approx. Principal Portion | Remaining Balance |
|---|---|---|---|
| Month 1 | 31.2% ($125.00) | 68.8% ($275.76) | $19,724 |
| Month 12 | 27.8% ($111.29) | 72.2% ($289.47) | $17,695 |
| Month 24 | 23.4% ($93.85) | 76.6% ($306.91) | $14,902 |
| Month 36 | 18.3% ($73.34) | 81.7% ($327.42) | $11,735 |
| Month 48 | 12.1% ($48.44) | 87.9% ($352.32) | $7,746 |
| Month 60 | 0.6% ($2.50) | 99.4% ($398.26) | $0 |
Types of Loans That Are Amortizing
Most consumer loans use standard amortization. Common types include:
- Personal loans — unsecured, 1-7 year terms, rates 6-36%.
- Auto loans — secured by vehicle, 24-84 month terms, rates 4-15%.
- Mortgages — 15 or 30 year terms, rates tied to 10-year Treasury yield.
- Student loans — federal rates set annually; standard 10-year repayment is fully amortizing.
- Home equity loans — lump-sum amount, fixed term, fully amortizing.
Non-amortizing structures include interest-only loans (balance unchanged during draw period), balloon loans (large final payment), and revolving credit like credit cards (minimum payment may not cover interest). Always confirm your loan type before using this calculator.
Amortization vs. Simple Interest
Simple interest calculates interest once on the original principal: Interest = P × R × T. Amortizing loans compound interest monthly on the outstanding balance. The practical effect is that amortizing loans always cost more than the equivalent simple-interest calculation for the same amount and rate, because interest is charged on the full balance during the early months before significant principal has been repaid.
Frequently Asked Questions
What is an amortization schedule?
An amortization schedule is a complete table of loan payments showing, month by month, how much of each payment goes toward interest and how much reduces the principal balance. In the early months the interest portion is high because the balance is large. As payments reduce the balance, interest shrinks and more goes to principal — even though the monthly payment stays constant. By the final payment, nearly the entire amount is principal.
How do extra monthly payments reduce my loan term?
Extra payments go 100% toward principal, which immediately reduces the balance on which future interest is calculated. Because interest is calculated on the outstanding balance each month, a lower balance means less interest — so more of every subsequent regular payment also goes to principal. On a $20,000 loan at 7.5% for 5 years, an extra $100/month saves roughly 8 months and about $400 in interest.
Why does early loan payoff save disproportionately more interest?
Interest is front-loaded in amortizing loans. In month 1 of a $20,000 loan at 7.5%, you pay $125 in interest. By month 55, you pay only about $15. Paying off the loan early eliminates all remaining interest charges — which, in the early years, are the largest charges. This is why paying off a loan in year 2 saves much more than twice as much interest as paying it off in year 4.
How is the monthly payment calculated?
The standard amortizing payment formula is: M = P × [r(1+r)^n] / [(1+r)^n − 1]. P is the principal, r is the monthly interest rate (annual rate ÷ 12), and n is the total number of payments. For a $20,000 loan at 7.5% for 5 years: r = 0.00625, n = 60, M = 20000 × [0.00625 × 1.453988] / [1.453988 − 1] = $400.76.
Does the amortization schedule change if I make irregular extra payments?
Yes. Each extra payment reduces the principal, which recalculates how much interest accrues the following month. The regular monthly payment stays the same, but the loan pays off faster. Banks recalculate the remaining schedule after each payment. This calculator shows the effect of a consistent extra monthly amount; for irregular lump-sum payments, use a dedicated extra-payment tracker.
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