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Amortization Calculator
Every loan payment is part principal, part interest, and the mix shifts every month. This amortization calculator builds the full schedule, marks the month principal finally overtakes interest, and prices what extra payments save.
See how this works on a $300,000 loan — 3 real examples
Monthly payment (principal & interest)
$0
Total interest
$0
Total paid
$0
Paid off
—
Principal overtakes interest
—
One payment, month by month
- Interest—
- Principal—
Principal vs interest: the crossover
Amortization scheduleMonth-by-month breakdown
| # | Date | Payment | Interest | Principal | Balance | Paid off |
|---|
How your amortization schedule is calculated
The fixed monthly payment comes from the standard loan-payment formula:
M = P · r(1 + r)n / ((1 + r)n − 1)
where P is the loan amount, r the monthly rate (annual rate ÷ 12) andn the number of payments (years × 12). The schedule then applies the amortization recurrence one month at a time:
interestt = balancet−1 × r · principalt = M + extra − interestt · balancet = balancet−1 − principalt
Assumptions worth knowing: the rate is fixed for the life of the loan and compounds monthly; extra payments start with payment #1 and are applied entirely to principal; the final payment is clamped so the balance lands exactly on zero (which is why the last row is smaller); a 0% loan simply divides the balance evenly (M = P ÷ n). Figures are principal and interest only — property tax, insurance, escrow and fees are excluded. All math runs at full precision and is only rounded for display.
One $300,000 loan on three different clocks
Same $300,000 at 6.5% every time. What changes is when the payment starts working for the borrower instead of the lender.
The standard schedule: 30 years at 6.5%
per month$1,896.20
- The first payment sends $1,625.00 to interest and only $271.20 to principal.
- Not until payment 233 — over nineteen years in — does principal claim more of the check than interest.
- By the finish, interest totals $382,633, well past the $300,000 that was borrowed.
A fixed payment whose insides shift for thirty years, most of that time in the lender's favor.
Load this example (opens in a new tab)The nudge: $200 extra on the same loan
per month$2,096.20
- Two hundred dollars more each month moves the crossover from payment 233 to payment 149 — seven years earlier.
- The final payment arrives at number 277 instead of 360, six years and eleven months ahead of schedule.
- All told, $103,449 of interest is never charged at all.
The required payment never changed; the $200 on top quietly rewrote the whole back half.
Load this example (opens in a new tab)The short clock: same loan over 15 years
per month$2,613.32
- The crossover shows up at payment 53 — under five years in, where the 30-year wait is over nineteen.
- Each month asks $717.12 more than the 30-year version.
- Total interest stops at $170,398, less than half of the 30-year figure of $382,633.
Half the term costs $717 more a month and skips $212,235 of interest.
Load this example (opens in a new tab)Illustrations only, not financial advice. Your own rate, taxes and insurance will differ — check with a qualified financial advisor before acting on any of this.
Reading your amortization schedule, in plain English
- Interest is front-loaded. Every payment is the same size, but early ones are mostly interest — on the default loan, $1,625 of the first $1,896 payment is interest and only $271 touches principal.
- The crossover comes late. Principal doesn’t overtake interest until payment 233 at 6.5% over 30 years — this calculator marks the exact month on the chart and highlights the row.
- Term beats rate. The same $300,000 at 6.5% costs ~$382,600 in interest over 30 years but ~$170,400 over 15 — a $212,000 gap for a higher monthly payment.
- Extra payments punch above their weight. $200/mo on the default loan saves ~$103,000 and finishes almost seven years early, because each extra dollar also cancels its future interest.
- Any fixed-rate loan works here. Auto, student, personal and business term loans follow the same math — set the amount, rate and term to match your note.
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Frequently asked questions
What is amortization?
Amortization is the process of paying off a debt with regular, equal payments that are split between interest and principal. Early payments are mostly interest; later payments are mostly principal. An amortization schedule is the table that shows that split, plus the remaining balance, for every payment until the loan reaches zero.
How is an amortization schedule calculated?
The monthly payment comes from the standard loan formula M = P·r(1+r)^n / ((1+r)^n − 1), where P is the amount borrowed, r the monthly rate and n the number of payments. Each month, interest equals the current balance times r; the rest of the payment reduces principal, and the new balance carries into the next month. Repeating that step n times produces the full schedule.
Why do I pay more interest at the beginning of the loan?
Because interest is charged on the outstanding balance, and the balance is largest at the start. On a $300,000 loan at 6.5%, the first payment of $1,896.20 includes $1,625.00 of interest — about 86% of it. As the balance falls, so does each month’s interest charge, freeing more of the same payment to pay down principal.
How do extra payments change my amortization schedule?
Extra payments go entirely to principal, which shrinks every future interest charge. Adding $200 a month to a $300,000, 30-year loan at 6.5% saves about $103,000 in interest and pays the loan off almost seven years early. Your required payment does not change — the term shortens instead.
When does principal first exceed interest on a mortgage?
Later than most people guess. At 6.5% on a 30-year loan the crossover lands at payment 233 — over 19 years in. The rate moves it a lot: at 5% it arrives near payment 195, at 7.5% near payment 250, and a 15-year term at 6.5% crosses around payment 53. This mortgage amortization schedule calculator highlights the exact month in both the chart and the schedule.
What is the difference between the amortization period and the loan term?
The amortization period is how long the payment schedule takes to reach a zero balance; the term is how long the loan contract lasts. For most US mortgages they are identical — a 30-year term amortized over 30 years. Balloon and many commercial loans differ: a loan might be amortized over 25 years but have a 5-year term, leaving a large balloon balance due at maturity.
Can I use this calculator for auto, student, or personal loans?
Yes. It doubles as a car loan amortization schedule calculator and works for any fixed-rate, fully amortizing loan — auto, student, personal, or a business term loan — which all follow the same math. Enter the amount, rate and term from your loan documents. It does not model revolving credit like credit cards or HELOC draw periods, where the balance and payment change month to month.
Disclaimer: these calculators are educational tools, not financial advice. They model your inputs with published formulas, but they cannot know your full situation — for decisions with real stakes, talk to a qualified professional. Formulas and defaults last reviewed .