🏠 Mortgage Calculator

Estimate principal, interest, taxes, insurance, PMI, HOA, total interest, and a first-year amortization preview.

Financial estimate note

Mortgage results are planning estimates, not lender quotes, affordability decisions, or financial advice.
Avoid entering personal identifiers; only scenario assumptions are needed.

Home price

Down payment

Interest rate %

Term years

Property tax / year

Insurance / year

PMI / month

HOA / month

Extra principal / month

Mortgage amortization checks

Builds a full month-by-month amortization schedule with taxes, insurance, PMI, HOA, optional extra principal, payoff timing, interest saved, and copyable CSV/JSON exports for deterministic API/MCP-safe calculator coverage.

Formula provenance

Version 2026-07-12 · implementation-derived from calculateMortgage

Formulas

loanAmount = max(0, homePrice - downPayment)monthlyRate = annualRate / 100 / 12principalInterest = loanAmount × monthlyRate / (1 - (1 + monthlyRate)^(-months))if monthlyRate = 0: principalInterest = loanAmount / months

monthlyTotal = principalInterest + annualPropertyTax / 12 + annualInsurance / 12 + monthlyPmi + monthlyHoa + monthlyExtraPayment

Variables and units

homePriceUSDdownPaymentUSDannualRatepercent per yeartermYearsyearsmonthsmonthsmonthlyRatedecimal per monthprincipalInterestUSD per monthmonthlyTotalUSD per month

Assumptions

Monthly compounding and monthly payments.
Term months are term years multiplied by 12 and rounded.
Extra payments reduce principal after scheduled principal.

Excluded

Lender underwriting and affordability rules
Closing costs and origination fees
Changing rates, taxes, insurance, PMI, or HOA
Tax deductions, legal advice, and lender quotes

Calculation: IEEE-754 JavaScript numbers; no intermediate display rounding
Display: Currency and percentages are generally shown to 2 decimal places

This describes the current deterministic implementation. It is not regulatory authority, a quote, or financial, tax, investment, medical, or legal advice.

{
  "version": "2026-07-12",
  "source": {
    "type": "implementation-derived",
    "authority": "Utilito deterministic core"
  },
  "rounding": {
    "calculation": "IEEE-754 JavaScript numbers; no intermediate display rounding",
    "display": "Currency and percentages are generally shown to 2 decimal places"
  },
  "advice": false,
  "tool_id": "mortgage-calculator",
  "core": {
    "module": "src/lib/mortgage-tax-core.mjs",
    "function": "calculateMortgage"
  },
  "formulas": [
    {
      "id": "loan-amount",
      "expression": "loanAmount = max(0, homePrice - downPayment)"
    },
    {
      "id": "monthly-rate",
      "expression": "monthlyRate = annualRate / 100 / 12"
    },
    {
      "id": "payment",
      "expression": "principalInterest = loanAmount × monthlyRate / (1 - (1 + monthlyRate)^(-months))"
    },
    {
      "id": "zero-rate-payment",
      "expression": "if monthlyRate = 0: principalInterest = loanAmount / months"
    },
    {
      "id": "monthly-total",
      "expression": "monthlyTotal = principalInterest + annualPropertyTax / 12 + annualInsurance / 12 + monthlyPmi + monthlyHoa + monthlyExtraPayment"
    }
  ],
  "variables": [
    {
      "name": "homePrice",
      "unit": "USD"
    },
    {
      "name": "downPayment",
      "unit": "USD"
    },
    {
      "name": "annualRate",
      "unit": "percent per year"
    },
    {
      "name": "termYears",
      "unit": "years"
    },
    {
      "name": "months",
      "unit": "months"
    },
    {
      "name": "monthlyRate",
      "unit": "decimal per month"
    },
    {
      "name": "principalInterest",
      "unit": "USD per month"
    },
    {
      "name": "monthlyTotal",
      "unit": "USD per month"
    }
  ],
  "assumptions": [
    "Monthly compounding and monthly payments.",
    "Term months are term years multiplied by 12 and rounded.",
    "Extra payments reduce principal after scheduled principal."
  ],
  "exclusions": [
    "Lender underwriting and affordability rules",
    "Closing costs and origination fees",
    "Changing rates, taxes, insurance, PMI, or HOA",
    "Tax deductions, legal advice, and lender quotes"
  ]
}

Scenario comparison

Compare 2 to 5 scenarios with the same deterministic formulas used by this calculator. Edit the JSON assumptions, then export a bounded CSV. No tax-law modeling or financial advice.

Scenario inputs

Values use USD and display rounding to two decimals. Compare assumptions, not just the largest result.

Sensitivity table

Vary one or two numeric inputs across at most 7 values per axis and 49 cells. Calculations reuse the unchanged formula core.

Sensitivity configuration JSON

Planning table only. Results use USD display assumptions, do not model tax law, and are not financial advice.

Runs in your browser

Mortgage estimates run locally in your browser. Shared links only include assumptions when you explicitly opt in.

Include current input in shared/debug payload

What this tool does

Mortgage Calculator estimates home loan payments and related affordability numbers from mortgage assumptions.

Why it is useful

It helps compare purchase prices, down payments, rates, terms, and rough monthly payment scenarios before deeper analysis.

How it works

The page applies mortgage payment formulas in the browser using the amount, interest rate, and term entered.

Best input

Use realistic loan amount, rate, term, property tax, insurance, HOA, PMI, and down payment assumptions when available.

Planning tip

Run conservative scenarios with higher rates or added costs so the result is not overly optimistic.

Privacy note

Mortgage estimates are calculated locally in your browser.

Important limitation

This is educational planning only, not mortgage, legal, tax, or financial advice. Real affordability depends on lender rules and your full situation.

Quick answers

Why is escrow missing or different?

Taxes, insurance, and HOA costs vary by property and lender.

Can this replace a lender quote?

No. Use it to compare scenarios before getting formal quotes.

API examples

Call the same deterministic core through Utilito’s compact API router. Send only data you intentionally submit to the server-side endpoint.

Try in API playground →Schema →

Estimate a mortgage payment with curl

curl

curl -X POST https://utilito.dev/api/run \
  -H "Content-Type: application/json" \
  -d '{"tool_id":"mortgage-calculator","input":{"price":500000,"downPayment":100000,"annualRate":6.75,"years":30,"tax":6000,"insurance":1800,"pmi":0,"hoa":0,"extraPayment":100}}'

Estimate a mortgage payment from JavaScript

javascript

const res = await fetch('https://utilito.dev/api/run', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    tool_id: 'mortgage-calculator',
    input: { price: 500000, downPayment: 100000, annualRate: 6.75, years: 30, tax: 6000, insurance: 1800, pmi: 0, hoa: 0, extraPayment: 100 }
  })
});
const data = await res.json();
console.log(data.result.output || data.result.report);

Estimate a mortgage payment from Python

python

import requests
payload = {
    "tool_id": "mortgage-calculator",
    "input": {"price": 500000, "downPayment": 100000, "annualRate": 6.75, "years": 30, "tax": 6000, "insurance": 1800, "pmi": 0, "hoa": 0, "extraPayment": 100},
}
result = requests.post("https://utilito.dev/api/run", json=payload).json()["result"]
print(result.get("output") or result.get("report"))

Common Use Cases

Estimate monthly mortgage payments before buying

Calculate principal, interest, taxes, and insurance estimates when house hunting.

Compare different mortgage scenarios

Test how different down payments, interest rates, or loan terms affect monthly costs.

Finance Calculator Suite workflow

Move between loan, mortgage, tax, household utility, compound growth, retirement, ROI, margin, sales-tax, and discount calculations while keeping assumptions and financial limitations visible per tab.

💳Loan Calculator 🧾Tax Estimator 💡Utility Cost Estimator 📈Compound Interest Calculator 🏦Retirement / FIRE Calculator 📈ROI Calculator

View all in Finance →