Mortgage Calculator Widget

Add a mortgage calculator that shows the whole monthly bill, not just principal and interest. Readers enter the home price, down payment and rate, plus tax, insurance, HOA dues and PMI, and see each part of the payment.

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<iframe src="https://a2z.tools/embed/w/mortgage-calculator" title="Mortgage Calculator by A2Z Tools" width="100%" height="830" style="border:0;width:100%" loading="lazy" allow="clipboard-write"></iframe>

A plain iframe. Works everywhere, including site builders that strip scripts. Adjust height if your content needs more room.

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How it works

Principal and interest use the same reducing-balance formula as the A2Z Mortgage Calculator, on the loan left after the down payment. Annual property tax and home insurance are divided by 12 and added, as are monthly HOA dues, giving the PITI-style figure a lender collects when it runs an escrow account. When the down payment is under 20% and a PMI rate is entered, PMI is charged on the original loan amount, and the widget walks the scheduled balance month by month to find when it first reaches 78% of the purchase price - the point at which US servicers must end borrower-paid PMI under the Homeowners Protection Act for loans on a principal residence closed since July 1999. The total interest line covers the full term with no prepayments.

Calculation method

  • Loan L = price - down payment (entered as % of price or as an amount)
  • P&I = L x r x (1 + r)^n / ((1 + r)^n - 1), r = rate / 12 / 100, n = years x 12
  • Monthly payment = P&I + property tax / 12 + insurance / 12 + HOA + PMI
  • PMI = L x PMI rate / 100 / 12, only when the down payment is under 20% of the price
  • PMI period = months until the scheduled balance is at or below 78% of the price (rounded up to a whole month)
  • Rounding: calculated unrounded, displayed to 2 decimals

Worked examples

400,000 home with 20% down

Inputs: Price 400,000; down 20%; 6.5% for 30 years; tax 4,800 a year; insurance 1,500 a year; no HOA

Result: Monthly payment 2,547.62 (P&I 2,022.62 + tax 400.00 + insurance 125.00); loan 320,000; total interest 408,142.36

No PMI because the down payment is 20%; interest over 30 years exceeds the loan itself.

350,000 home with 10% down and PMI

Inputs: Price 350,000; down 10%; 6.5% for 30 years; tax 4,200; insurance 1,200; PMI 0.6% a year

Result: Monthly payment 2,598.51 including PMI 157.50 for about 109 months; P&I 1,991.01 on a 315,000 loan

PMI stops once the scheduled balance falls to 273,000 (78% of the price), a little over 9 years in.

Adding HOA dues

Inputs: Price 400,000; 20% down; 6.5% for 30 years; tax 4,800; insurance 1,500; HOA 350 a month

Result: Monthly payment 2,897.62 (HOA 350.00 of it)

Condominium and townhouse dues sit outside the loan but inside the monthly budget.

Limitations

  • Uses the purchase price as the home's 'original value'; the law uses the lower of price and appraised value.
  • Does not apply the midpoint rule or lender-specific PMI terms, and treats PMI as a flat percentage of the original loan.
  • Property tax, insurance and HOA dues are held constant; in practice they are reassessed and usually rise.
  • Fixed-rate loans only: adjustable-rate mortgages, discount points, closing costs and FHA or VA mortgage insurance and funding fees are not modelled.
  • Escrow cushions, annual escrow analysis shortages and flood or earthquake cover are outside the figure.

Where publishers use it

  • Estate agents' listing pages showing a realistic monthly cost next to the price
  • Mortgage brokers' sites for first-time buyers comparing down-payment sizes
  • Home-buying guides explaining PITI and when PMI drops off
  • Relocation blogs comparing housing costs between cities with different tax rates
  • Homebuilders' new-construction pages quoting an all-in monthly figure for each floor plan
  • Condominium and planned-community sites showing how monthly association dues change what a buyer can borrow

Questions

What does PITI mean?

Principal, interest, taxes and insurance - the four parts of a typical monthly mortgage payment when the lender collects tax and insurance through escrow. This widget adds HOA dues and PMI when they apply.

When does PMI stop?

The CFPB explains that you can ask your servicer to cancel PMI when the balance is scheduled to reach 80% of the home's original value, that it must end automatically at 78%, and that it must also end the month after the loan's midpoint. The widget estimates the 78% date from the normal schedule; extra payments or a new appraisal can end it sooner.

Where do I find my property tax figure?

Use the annual tax on the listing or the county assessor's site. Rates differ widely by county, so an estimate from another area can be far off.

Why does a 10% down payment cost more than the extra loan interest?

Beyond the larger loan, PMI is added: on a 350,000 home with 10% down and PMI at 0.6% a year, that is 157.50 a month for about 109 months, over 17,000 in total.

How much does a 15-year term save over 30 years?

On a 320,000 loan at 6.5%, the 15-year principal and interest is 2,787.54 a month against 2,022.62, but total interest falls from 408,142.36 to 181,757.84. Try both terms in the widget with your own rate.

What does one percentage point on the rate cost?

On the same 320,000 loan over 30 years, going from 6.5% to 7.5% raises principal and interest from 2,022.62 to 2,237.49 a month and lifetime interest by about 77,000.

Does the 78% rule apply to FHA loans?

No. It covers conventional borrower-paid PMI. Government-backed loans such as FHA charge their own mortgage insurance premium with separate cancellation terms, so enter that premium in the PMI box but ignore the stop date.

Can readers outside the US use it?

Yes: leave PMI and HOA empty, put council or municipal property tax in the tax box and buildings insurance in the insurance box. The monthly principal-and-interest figure is the same maths everywhere; only the PMI note is US-specific.

How much do HOA dues change affordability?

Dues are paid every month on top of the mortgage, so lenders count them in your debt-to-income ratio. On the 400,000 example, 350 of monthly dues lifts the payment from 2,547.62 to 2,897.62 - the same as borrowing tens of thousands more.

What are discount points?

Upfront fees, each usually 1% of the loan, paid to buy a lower rate. The widget does not add points to the loan; compare the payment at each quoted rate and divide the points' cost by the monthly saving to find the break-even month.

Why might my Loan Estimate show a different monthly figure?

The lender's escrow uses its own tax and insurance estimates, may add an initial escrow cushion, and quotes PMI from an insurer's rate card based on credit score and LTV. Replace the widget's tax, insurance and PMI inputs with the Loan Estimate figures to reconcile the two.

Sources

  1. When can I remove private mortgage insurance (PMI) from my loan? - Consumer Financial Protection Bureau (US) . 80% request, 78% automatic termination and midpoint rules for single-family principal residences closed on or after 29 July 1999 (Homeowners Protection Act). Checked 2026-10-01.
  2. What is amortization and how could it affect my loan? - Consumer Financial Protection Bureau (US) . Reducing-balance schedule used for the P&I figure and the 78% date.

Cite or recommend this tool

If you reference this tool in an article, course or documentation, these formats are ready to copy. They are optional - nothing is added to your site unless you paste it.

A2Z Tools Mortgage Calculator
https://a2z.tools/mortgage-calculator

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