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Amortization Calculator

This amortization calculator gives the full month-by-month schedule and the split every payment makes between interest and principal. The landmark worth knowing is when principal finally overtakes interest: on a 30-year loan that arrives long after the halfway point.

Example numbers

30 years

In months. 360 is 30 years.

Applied to principal in the month it is paid, which shortens the term.

Result

The answerfrom an example

Most of your payment is interest until month 233, 19 years, 5 months into a 30 years loan.

Worked on $300,000 at 6.50% over 30 years. Change anything below to use yours.

Monthly payment
$1,896.20
Principal overtakes interest
Month 233
Interest in year one
$19,401

The figures behind it

Monthly payment
$1,896.20
The level scheduled payment.
Principal overtakes interest
Month 233
19 years, 5 months in. Before then, most of each payment is interest.
Interest in year one
$19,401
85.3% of everything paid in the first twelve months, against $3,353 of principal.
Total interest
$382,637
Over the life of the loan.
Total repaid
$682,637
Principal and interest together.
Paid off in
30 years
The full scheduled term.
Everything you repay$682,637
  • PrincipalThe amount borrowed.$300,000
  • InterestThe cost of borrowing it.$382,637

How each payment splits, month by month

Net worth over time under both scenariosInterest portion ends at $10. Principal portion ends at $1.9K. The same figures appear in the payment schedule below.$0$500$1K$1.5K$2K051015202530Principal overtakes interest · year 19

Years from today

Interest portionPrincipal portion
Payment scheduleShow

The table scrolls sideways

MonthPaymentInterestPrincipalBalanceInterest to date
3$1,896.20$1,622.05$274.15$299,182$4,871
6$1,896.20$1,617.57$278.63$298,351$9,728
9$1,896.20$1,613.02$283.18$297,506$14,571
12$1,896.20$1,608.40$287.80$296,647$19,401
15$1,896.20$1,603.69$292.51$295,774$24,217
18$1,896.20$1,598.92$297.28$294,887$29,019
21$1,896.20$1,594.06$302.14$293,985$33,806
24$1,896.20$1,589.12$307.08$293,069$38,578
27$1,896.20$1,584.10$312.10$292,138$43,335
30$1,896.20$1,579.01$317.19$291,191$48,077
33$1,896.20$1,573.82$322.38$290,230$52,804
36$1,896.20$1,568.56$327.64$289,252$57,515
39$1,896.20$1,563.20$333.00$288,258$62,210
42$1,896.20$1,557.76$338.44$287,248$66,889
45$1,896.20$1,552.23$343.97$286,222$71,551
48$1,896.20$1,546.61$349.59$285,179$76,197
51$1,896.20$1,540.90$355.30$284,119$80,825
54$1,896.20$1,535.10$361.10$283,041$85,436
57$1,896.20$1,529.20$367.00$281,946$90,030
60$1,896.20$1,523.20$373.00$280,833$94,605
63$1,896.20$1,517.11$379.09$279,702$99,163
66$1,896.20$1,510.91$385.29$278,552$103,702
69$1,896.20$1,504.62$391.58$277,384$108,222
72$1,896.20$1,498.22$397.98$276,197$112,723
75$1,896.20$1,491.72$404.48$274,990$117,205
78$1,896.20$1,485.11$411.09$273,763$121,667
81$1,896.20$1,478.39$417.81$272,516$126,108
84$1,896.20$1,471.57$424.63$271,249$130,530
87$1,896.20$1,464.63$431.57$269,961$134,931
90$1,896.20$1,457.58$438.62$268,653$139,311
93$1,896.20$1,450.41$445.79$267,322$143,669
96$1,896.20$1,443.13$453.07$265,971$148,006
99$1,896.20$1,435.73$460.47$264,597$152,320
102$1,896.20$1,428.20$468.00$263,200$156,613
105$1,896.20$1,420.56$475.64$261,781$160,882
108$1,896.20$1,412.79$483.41$260,338$165,128
111$1,896.20$1,404.89$491.31$258,872$169,351
114$1,896.20$1,396.86$499.34$257,382$173,549
117$1,896.20$1,388.70$507.50$255,868$177,724
120$1,896.20$1,380.41$515.79$254,329$181,873
123$1,896.20$1,371.98$524.22$252,765$185,998
126$1,896.20$1,363.42$532.78$251,175$190,096
129$1,896.20$1,354.71$541.49$249,559$194,169
132$1,896.20$1,345.87$550.33$247,917$198,216
135$1,896.20$1,336.88$559.32$246,248$202,235
138$1,896.20$1,327.74$568.46$244,552$206,228
141$1,896.20$1,318.45$577.75$242,828$210,192
144$1,896.20$1,309.01$587.19$241,076$214,129
147$1,896.20$1,299.42$596.78$239,295$218,037
150$1,896.20$1,289.67$606.53$237,486$221,916
153$1,896.20$1,279.76$616.44$235,646$225,765
156$1,896.20$1,269.68$626.52$233,777$229,584
159$1,896.20$1,259.45$636.75$231,877$233,373
162$1,896.20$1,249.05$647.15$229,946$237,130
165$1,896.20$1,238.47$657.73$227,983$240,856
168$1,896.20$1,227.73$668.47$225,989$244,550
171$1,896.20$1,216.80$679.40$223,961$248,212
174$1,896.20$1,205.70$690.50$221,901$251,840
177$1,896.20$1,194.42$701.78$219,807$255,434
180$1,896.20$1,182.96$713.24$217,679$258,995
183$1,896.20$1,171.30$724.90$215,516$262,520
186$1,896.20$1,159.46$736.74$213,317$266,011
189$1,896.20$1,147.42$748.78$211,083$269,465
192$1,896.20$1,135.19$761.01$208,812$272,883
195$1,896.20$1,122.76$773.44$206,505$276,264
198$1,896.20$1,110.12$786.08$204,159$279,607
201$1,896.20$1,097.28$798.92$201,775$282,911
204$1,896.20$1,084.22$811.98$199,352$286,177
207$1,896.20$1,070.96$825.24$196,890$289,403
210$1,896.20$1,057.47$838.73$194,387$292,589
213$1,896.20$1,043.77$852.43$191,844$295,734
216$1,896.20$1,029.84$866.36$189,259$298,838
219$1,896.20$1,015.69$880.51$186,631$301,899
222$1,896.20$1,001.30$894.90$183,961$304,917
225$1,896.20$986.68$909.52$181,247$307,892
228$1,896.20$971.82$924.38$178,489$310,823
231$1,896.20$956.72$939.48$175,686$313,708
234$1,896.20$941.37$954.83$172,837$316,547
237$1,896.20$925.77$970.43$169,941$319,340
240$1,896.20$909.91$986.29$166,998$322,086
243$1,896.20$893.80$1,002.40$164,007$324,784
246$1,896.20$877.42$1,018.78$160,967$327,432
249$1,896.20$860.78$1,035.42$157,877$330,031
252$1,896.20$843.86$1,052.34$154,737$332,580
255$1,896.20$826.67$1,069.53$151,546$335,077
258$1,896.20$809.19$1,087.01$148,303$337,522
261$1,896.20$791.43$1,104.77$145,006$339,914
264$1,896.20$773.38$1,122.82$141,656$342,253
267$1,896.20$755.04$1,141.16$138,251$344,536
270$1,896.20$736.39$1,159.81$134,790$346,764
273$1,896.20$717.45$1,178.75$131,273$348,935
276$1,896.20$698.19$1,198.01$127,698$351,049
279$1,896.20$678.61$1,217.59$124,065$353,105
282$1,896.20$658.72$1,237.48$120,372$355,101
285$1,896.20$638.50$1,257.70$116,620$357,037
288$1,896.20$617.95$1,278.25$112,806$358,911
291$1,896.20$597.07$1,299.13$108,929$360,723
294$1,896.20$575.84$1,320.36$104,989$362,472
297$1,896.20$554.27$1,341.93$100,985$364,157
300$1,896.20$532.35$1,363.85$96,916$365,776
303$1,896.20$510.06$1,386.14$92,780$367,328
306$1,896.20$487.42$1,408.78$88,576$368,813
309$1,896.20$464.40$1,431.80$84,304$370,230
312$1,896.20$441.01$1,455.19$79,962$371,576
315$1,896.20$417.23$1,478.97$75,549$372,852
318$1,896.20$393.07$1,503.13$71,063$374,055
321$1,896.20$368.51$1,527.69$66,505$375,185
324$1,896.20$343.55$1,552.65$61,872$376,241
327$1,896.20$318.18$1,578.02$57,164$377,221
330$1,896.20$292.40$1,603.80$52,378$378,124
333$1,896.20$266.20$1,630.00$47,514$378,949
336$1,896.20$239.57$1,656.63$42,571$379,694
339$1,896.20$212.50$1,683.70$37,547$380,359
342$1,896.20$184.99$1,711.21$32,441$380,942
345$1,896.20$157.03$1,739.17$27,252$381,441
348$1,896.20$128.62$1,767.58$21,978$381,855
351$1,896.20$99.74$1,796.46$16,617$382,183
354$1,896.20$70.39$1,825.81$11,169$382,424
357$1,896.20$40.56$1,855.64$5,632$382,576
360$1,900.91$10.24$1,890.67$0$382,637

What this result assumes

  • Rows are shown every third month to keep the table readable; the CSV export carries the same rows.
  • Interest is charged on the balance outstanding at the start of each month and rounded to the cent, exactly as a servicer would. The final payment absorbs the accumulated rounding so the balance lands on precisely zero.
  • The rate is treated as a nominal annual rate compounded monthly, which is how US consumer loans and mortgages are quoted.
  • Escrowed property tax and insurance are not included. This is the loan alone.

Methodology

Reviewed

How a level payment splits

The payment never changes, but what it buys does. Each month interest is charged on the balance outstanding at the start of that month, and whatever is left of the payment reduces the principal. Because the balance is largest at the beginning, so is the interest — and the principal portion is correspondingly small.

On $300,000 at 6.5% over thirty years the payment is $1,896.20 throughout. In the first month about $1,625 of that is interest and only $271 touches the balance. In the final month it is almost entirely principal. Nothing about the payment changed; only the balance it is charged against did.

The month those two portions cross over is the landmark this calculator marks, and it is much later than most people expect: past month 200 on the default figures, well beyond the halfway point of the term. It is the single clearest illustration of why overpaying early is worth so much more than overpaying late.

The arithmetic

The level payment is the standard amortization formula, M = P × [r(1 + r)ⁿ] ÷ [(1 + r)ⁿ − 1], where P is the amount borrowed, n the term in months and r the annual rate divided by twelve. US loans quote a nominal annual rate compounded monthly, so r is a plain division rather than an effective-rate conversion.

Interest is rounded to the cent each month, exactly as a servicer would, and the final payment absorbs whatever rounding remainder has accumulated so the balance lands on precisely zero. The test suite asserts that the principal repaid across the whole schedule equals the amount borrowed to the cent — a 360-month table cannot drift.

At a 0% rate the formula is undefined, so the balance is divided evenly across the term instead. There is then no crossover, because there is no interest to overtake.

What an extra payment does to the shape

Every extra dollar goes entirely to principal and stops accruing interest for the whole remaining term — so it is not earning the rate for one month, it is avoiding the rate for years. That is why a modest monthly overpayment moves the payoff date so much further than it seems it should.

It also pulls the crossover month forward, which the chart shows directly. Enter an amount in the extra field and watch both the marker and the payoff date move.

One practical caveat the arithmetic cannot capture: some servicers apply an unallocated overpayment to your next scheduled payment rather than to principal. That advances your due date without shortening the term or saving a cent of interest. If you intend to overpay, say in writing that it is to be applied to principal.

Assumptions

  • The interest rate is fixed for the whole term.
  • The rate entered is a nominal annual rate compounded monthly, as US loans are quoted.
  • Payments are made in full and on time every month.
  • Extra payments reduce principal in the month they are made and shorten the term rather than lowering the payment.
  • Escrowed property tax, hazard insurance and mortgage insurance are excluded — this is the loan alone.
  • Origination fees, points and closing costs are excluded, so the true APR of a fee-bearing loan is higher than the rate entered.
  • No prepayment penalty, late fee, forbearance or recast is modelled.
  • Every figure is nominal. Inflation is ignored.

Sources

Common questions

What is an amortization schedule?
A month-by-month table showing how each payment divides between interest and principal, and what the balance is afterwards. It matters because the split is not constant: on a 30-year loan at 6.5%, the first payment is roughly 86% interest and the last is almost entirely principal, even though the payment itself never changes.
Why is most of my early mortgage payment interest?
Because interest is charged on the balance you still owe, and at the start that balance is at its largest. The payment is level, so whatever interest takes, principal does not get. As the balance falls, the interest charge falls with it and more of the same payment reaches the principal, which is why the split shifts steadily across the term.
When does principal exceed interest on a 30-year mortgage?
Later than most people expect, past month 200 of 360 on a loan at 6.5%. The calculator marks the exact month for your numbers and shows it on the chart. The higher the rate, the later the crossover; paying extra brings it forward.
How much does paying extra actually save?
More than it looks, because an extra dollar avoids interest for every remaining month rather than just one. Enter an amount in the extra field and the calculator reports the interest saved and how much earlier the loan clears. Whether that is the best use of the money is a separate question, paying the mortgage down versus investing works out the bar it has to beat.
Does this include property tax and insurance?
No. This is the loan on its own. For the full housing payment with escrowed tax, insurance and PMI, use the mortgage calculator; for a car, the auto loan calculator handles sales tax and a trade-in.
Can I use this for a car loan or personal loan?
Yes, the arithmetic is identical for any level-payment instalment loan. Only the term and rate differ. The loan calculator is the same engine with a shorter table and a focus on the interest share rather than the schedule.

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