Mortgage Amortization Calculator with Extra Payments

How is a mortgage payment calculated?

Principal and interest come from the annuity formula: P&I = L × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1), where L is the loan, r is the annual rate divided by 12 and n is the number of monthly payments. Take the starter-home preset: $350,000 with 10% down leaves a $315,000 loan. At 6.75% over 30 years, r is 0.005625 and n is 360, and the payment comes to $2,043.08.

The payment never changes on a fixed-rate loan, but its split does. Each month's interest is the remaining balance times r, so payment one sends $1,771.88 to the lender as interest and only $271.21 to principal. The balance falls a little, next month's interest falls with it, and principal picks up the difference. Across all 360 payments that loan carries $420,510 of interest on $315,000 borrowed.

What is PITI? Your payment with taxes and insurance

PITI is what a mortgage payment calculator with taxes and insurance adds up: principal, interest, property taxes and homeowners insurance, usually collected together through an escrow account. On the starter preset, P&I of $2,043.08 picks up $320.83 of property tax (1.1% of the price), $116.67 for a $1,400 insurance policy and $144.38 of PMI. The monthly check is $2,624.96, roughly 28% more than the P&I number a rate quote leads with.

Location moves the tax line more than anything else. The Tax Foundation's analysis of 2024 Census data puts the average effective property tax rate on owner-occupied homes at 0.90%, with New Jersey and Illinois at 1.88% and Hawaii at 0.29%. On a $500,000 house that is $1,450 a year in Hawaii against $9,400 in New Jersey. The high-tax-state preset uses 1.9%, and tax alone becomes $791.67 of a $3,536.06 monthly payment. HOA dues are not part of PITI in the lending sense, but they are due every month, so they are added to the total.

Mortgage amortization schedule: interest vs principal over time

Open the monthly view of the mortgage amortization schedule calculator above and the first 237 rows share one trait: interest is the larger slice of every payment. On the $315,000 loan at 6.75%, principal finally overtakes interest at payment 238, almost 20 years in. Year one alone sends $21,160 to interest and $3,357 to principal.

The chart works as a mortgage interest vs principal calculator: red is interest paid per year, green is principal, the dashed white line is the balance on the original schedule and the dashed purple line is the balance with your extra payments. The green marker is the crossover year and the blue one is the year PMI drops. Sort the table by the interest column or filter a single year to see exactly where the money went, then export all 360 rows as CSV.

Extra payment mortgage calculator: what each extra dollar buys

The usual question is how much extra to pay off mortgage faster, and the answer on the starter loan is smaller than most people expect. An extra $100 a month saves $65,662 of interest and finishes 3 yr 11 mo sooner. At $250 the savings reach $129,864 and 7 yr 11 mo. At $500 they are $194,555 and 12 yr 3 mo, and $1,000 a month saves $261,947 and cuts 17 years.

Extra principal also moves the PMI date. Adding $200 a month to the starter loan brings the 80% point from payment 98 to payment 63, nearly three years of PMI you stop paying. A one-time lump sum works too: $20,000 applied in month 13 saves $98,799 and cuts 4 yr 10 mo. Whether that cash should go to the mortgage at all depends on what else it could earn, which the payoff-vs-invest comparison scores on a risk-adjusted basis.

Biweekly mortgage calculator: does paying every two weeks work?

A year has 52 weeks, so half-payments every two weeks add up to 26 halves, or 13 full payments. That thirteenth payment is the whole trick. Toggle biweekly mode and the calculator adds one-twelfth of your P&I to principal each month: $170.26 on the starter loan, which saves $99,370 of interest and ends the loan 6 years sooner.

Paying someone to run it for you is rarely worth it. In 2015 the CFPB sued Nationwide Biweekly Administration, alleging the company misled borrowers about the savings from its program while charging a setup fee of up to $995 plus ongoing processing fees. Some third-party programs also hold your half-payments and forward one full payment a month, in which case nothing is saved between the halves. Adding the extra one-twelfth yourself costs nothing and gets the same result.

When does PMI drop off? What the PMI removal calculator checks

Three dates matter under the Homeowners Protection Act, as the CFPB summarizes it. You can request cancellation in writing once the balance reaches 80% of the home's original value, meaning the lower of the purchase price or the appraisal, and extra payments that get you there early count. The servicer must cancel automatically when the balance is scheduled to reach 78% on the original amortization schedule. And PMI must end no later than the month after the loan's midpoint, which is month 181 of a 30-year loan.

The tool reports the first two separately because the gap costs real money. On the starter home the 80% request point comes after payment 98, and total PMI is $14,149 if you ask then. Wait for the automatic 78% date after payment 112 and you pay $2,021 more. A request also needs a good payment history, no second liens, and sometimes an appraisal showing the home has not lost value. The model assumes conventional borrower-paid PMI, which Freddie Mac's homebuyer guidance puts at roughly $30 to $70 a month per $100,000 borrowed. FHA mortgage insurance follows its own rules.

15 year vs 30 year mortgage calculator: what the shorter term buys

Shorter loans are cheaper twice: the rate is lower and you borrow for half as long. Freddie Mac's survey for the week of September 10, 2026 put the 30-year average at 6.76% and the 15-year at 6.09%, a 0.67-point spread, and the comparison panel prices the other term with that spread. For the $315,000 starter loan at 6.75%, the 15-year at 6.08% costs $2,671.78 a month in principal and interest, $628.70 more than the 30-year.

That extra $628.70 saves $254,589 of interest over the life of the loan, and PMI ends after payment 31 instead of 98 because the balance falls so much faster. The 30-year still has one real advantage: its required payment is lower, so a job loss or a lean year does not become a missed payment. Borrowers who want both often take the 30-year and prepay on a 15-year pace, which the extra-payment panel models directly.

Home equity build calculator: how fast you own the house

Equity here means the price minus what you still owe, counting your down payment and ignoring appreciation, so it measures only what the loan has returned to you. On the starter loan you own 15.5% of the house after five years, and just 5.5 points of that came from payments; the other 10 points were the down payment. The move-up preset at 20% down reaches 25.1% in the same five years. The Equity column in the schedule and the equity-at-year-5 figure in the presentation view (press E) track the number month by month.

How much house can you afford? The 28/36 rule

The long-standing rule of thumb caps housing at 28% of gross monthly income and all debt payments at 36%. Enter your income in the Affordability panel and the guardrail plots both ratios against those lines. With $9,500 of gross monthly income, 28% is $2,660, so the $2,624.96 starter PITI sits at 27.6%, and another $600 of monthly debt takes the total to 34.0%.

Approval limits are looser than the rule. Fannie Mae's Selling Guide allows 36% total debt on manually underwritten loans, up to 45% with strong credit and reserves, and up to 50% through Desktop Underwriter, and the CFPB dropped the old 43% cap from its general Qualified Mortgage definition in 2021. Reaching the ceiling is a different thing from being comfortable. If renting is still on the table, the rent vs buy calculator compares the full cost of both paths.

Mortgage payoff date calculator: work backward from a target

The reverse calculator answers three planning questions. Pick a target year and it returns the constant extra payment that retires the loan on time: finishing the $315,000, 6.75% loan in 20 years takes $352.06 a month and saves $160,675 of interest. Enter a monthly budget and it returns the price that fits it, holding your down payment, rate, term and tax and insurance ratios; $2,500 a month on the starter assumptions supports $333,339. Enter the cash you have and it shows the most home that cash covers at 20% down with no PMI, so $80,000 points to $400,000.

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