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Mortgage Payment Calculator

Computes the monthly principal-and-interest payment of a fixed-rate mortgage from home price, down payment, rate and term, then adds property tax, home insurance and HOA dues to give the full monthly housing payment and lifetime interest.

When to use

You want the monthly cost of buying a home with a fixed-rate mortgage, including escrowed taxes and insurance, or the total interest over the loan.

Do not use when: The loan is adjustable-rate or interest-only, or you only need the payment on a plain loan amount (use loan-payment).

Formula

loan_amount = home_price − down_payment; i = annual_rate_percent / 1200; n = 12·term_years; P&I = loan_amount × i / (1 − (1 + i)^−n) (loan_amount / n if i = 0); total_monthly_payment = P&I + annual_property_tax/12 + annual_home_insurance/12 + monthly_hoa.

Standard fixed-rate amortization with monthly compounding. Private mortgage insurance, closing costs and escrow cushions are not included; add PMI (typically 0.5–1.5 % of the loan per year) to the total when loan_to_value_percent exceeds 80 %.

Inputs

Parameter	Type	Unit	Required	Description
`home_price`	number		yes	Purchase price of the property. Range: > 0, ≤ 1000000000000
`down_payment`	number		default 0	Cash paid up front; loan_amount = home_price − down_payment. For 20 % of a 250,000 home enter 50000. Range: ≥ 0, ≤ 1000000000000
`annual_rate_percent`	number	%	yes	Fixed note rate in percent; the monthly rate is this / 12. Range: ≥ 0, ≤ 100
`term_years`	number	years	default 30	Loan term in years (30 and 15 are the common US terms). Range: > 0, ≤ 50
`annual_property_tax`	number		default 0	Yearly property tax; one twelfth is added to the monthly payment. Range: ≥ 0, ≤ 1000000000
`annual_home_insurance`	number		default 0	Yearly homeowners insurance premium; one twelfth is added monthly. Range: ≥ 0, ≤ 1000000000
`monthly_hoa`	number		default 0	Monthly homeowners-association or condo fee. Range: ≥ 0, ≤ 10000000

Outputs

Output	Type	Unit	Description
`loan_amount`	number		home_price − down_payment.
`loan_to_value_percent`	number	%	loan_amount / home_price × 100; above 80 % usually requires mortgage insurance (PMI).
`monthly_principal_and_interest`	number		Level monthly amortizing payment on the loan.
`monthly_property_tax`	number		annual_property_tax / 12.
`monthly_insurance`	number		annual_home_insurance / 12.
`monthly_hoa_fee`	number		monthly_hoa as entered.
`total_monthly_payment`	number		Principal & interest + tax + insurance + HOA (PITI + HOA).
`number_of_payments`	integer		12 × term_years.
`total_interest`	number		Interest paid over the full term.
`total_of_payments`	number		monthly_principal_and_interest × number_of_payments.
`payoff_summary`	string		Plain-language summary of the loan schedule.

Example

250,000 home, 50,000 down, 6 % for 30 years, 3,000 tax, 1,200 insurance: {"home_price":250000,"down_payment":50000,"annual_rate_percent":6,"term_years":30,"annual_property_tax":3000,"annual_home_insurance":1200} → {"loan_amount":200000,"loan_to_value_percent":80,"monthly_principal_and_interest":1199.1,"monthly_property_tax":250,"monthly_insurance":100,"total_monthly_payment":1549.1,"number_of_payments":360,"total_interest":231676.38,"total_of_payments":431676.38}

400,000 home, 80,000 down, 6.5 % for 30 years: {"home_price":400000,"down_payment":80000,"annual_rate_percent":6.5,"term_years":30} → {"loan_amount":320000,"monthly_principal_and_interest":2022.62,"total_monthly_payment":2022.62,"total_interest":408142.36}

GET https://tttkmbb.com/api/v1/calculate/mortgage-payment?home_price=250000&down_payment=50000&annual_rate_percent=6&term_years=30&annual_property_tax=3000&annual_home_insurance=1200

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/mortgage-payment (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/mortgage-payment · Markdown: https://tttkmbb.com/finance/mortgage-payment.md · JSON definition: https://tttkmbb.com/finance/mortgage-payment.json
MCP: server https://tttkmbb.com/mcp, tool calculate_mortgage_payment
OpenAPI operationId: calculate_mortgage_payment
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

CFPB – Owning a Home: loan costs and monthly payment components (government)
Wikipedia – Amortization calculator (annuity payment formula) (reference)

FAQ

What does PITI mean?

Principal, Interest, Taxes and Insurance: the four components lenders count as the housing payment. total_monthly_payment is PITI plus any HOA dues.

Why is my lender's quote slightly different?

Lenders round the payment to cents, may include PMI or an escrow cushion, and property tax and insurance change every year while this calculator holds them constant.

How does a 15-year term compare?

Set term_years=15: the monthly payment rises but total interest falls sharply (200,000 at 6 % costs 231,676 interest over 30 years but 103,788 over 15 years).

Related calculators

Loan Payment Calculator — Bare amortization without taxes and insurance.
Debt Payoff Calculator — See how extra monthly payments shorten the loan.
Compound Interest Calculator — Compare with investing the down payment instead.