Mortgage Calculator

Estimate monthly payment and a simple breakdown (principal & interest, taxes, insurance, HOA, optional PMI). Start with a fast snapshot, add detail only if you want it, then stress-test scenarios.

For educational purposes only. This calculator provides general estimates and does not provide financial, trading, tax, or legal advice.

Runs locally in your browser. No account. No signups.

Fast Payment Snapshot

Enter the core inputs to estimate principal & interest and an optional monthly add-on breakdown. This is arithmetic from your inputs, not a recommendation.

Used to compute loan amount (price − down payment).
Leave blank for $0, or use Add detail for %.
Used for a standard fixed-rate amortization estimate.
Common terms are 15 or 30 years, but any positive term works for the math.
Converted to monthly (annual ÷ 12) for the estimate.
Converted to monthly (annual ÷ 12) for the estimate.
Added to the total monthly estimate if entered.
If you prefer PMI as a rate, use Add detail.
Educational estimates only. This mortgage calculator performs standard amortization math based on user-entered values and simplified assumptions (including loan amount, interest rate, term length, and optional taxes, insurance, HOA, or PMI inputs if provided). It does not provide personalized financial, mortgage, tax, or legal advice. Results are not guarantees and may differ from real-world loan terms due to lender fees, closing costs, points, escrow rules, rate changes, PMI requirements, underwriting, rounding, or product-specific details. Calculations run locally in your browser. Verify numbers independently before acting. See Disclaimer, Privacy Policy, and Terms of Use.

How This Mortgage Calculator Works

The core estimate uses a standard fixed-rate amortization model to calculate the monthly principal & interest payment based on loan amount, interest rate, and term. Optional monthly add-ons (taxes, insurance, HOA, and PMI if provided) are then added to show a broader monthly payment estimate.

Quick Example (Illustrative Only)

Suppose a home price of $420,000 with a down payment of $84,000 (loan $336,000), at 6.75% for 30 years. If property taxes are $4,200/year and insurance is $1,600/year, those convert to $350/month and $133.33/month.

  • Principal & interest: computed from the loan amortization formula
  • Estimated monthly add-ons: taxes + insurance (+ HOA/PMI if entered)
  • Total monthly estimate: P&I + add-ons

What the Breakdown Means

  • Principal & interest (P&I): the loan payment from the amortization formula.
  • Taxes & insurance: optional estimates converted to a monthly equivalent.
  • HOA: optional monthly amount added as entered.
  • PMI: optional. If entered as a monthly amount, that is used; otherwise the tool can estimate from a yearly PMI rate.
Escrow note: some lenders collect taxes and insurance through escrow and may add cushions or adjust amounts over time. This tool uses simple monthly equivalents for comparison.
Limits: results are estimates. Real payments can differ due to loan program rules, fees, rounding, tax and insurance changes, and timing.

Data & Privacy (Local-Only)

This calculator runs locally in your browser. Your entries are not submitted as form data and are not stored by FinFormulas for signups. For site-wide policies, see the Privacy Policy.

Understanding the Mortgage Payment Components

Many people hear “mortgage payment” and assume it always means a single number. In practice, monthly housing costs can include multiple parts. This calculator separates them so you can see how the structure changes when you vary inputs.

Principal and interest are the amortized loan payment

The principal & interest payment is the fixed-rate amortization result for a given loan amount, interest rate, and term. Early in the schedule, interest tends to be a larger share of the P&I payment; later, principal tends to become a larger share. The calculator’s “total interest” estimate is based on this P&I model only (excluding taxes/insurance/HOA/PMI).

Taxes and insurance are often treated as monthly equivalents

Property taxes and homeowners insurance can be paid in different ways. Some setups treat them as an estimated monthly equivalent (annual ÷ 12), sometimes with escrow practices that can adjust over time. In this tool, tax and insurance inputs are included only if you provide them, and they are used as simple monthly equivalents.

HOA and PMI are add-ons (when applicable)

HOA dues are added as entered (monthly). PMI is optional and is included only if you enter it (as a monthly amount or as a percent-of-loan annual rate in Add detail / Stress test). Because PMI rules vary by loan program and lender, the PMI portion here is best treated as a scenario input rather than a universal assumption.

Interpretation: the most useful comparisons usually hold everything constant and change one variable at a time (rate, down payment, taxes, insurance), then compare the output.

Why Interest Rate and Term Create Big Swings

Interest rate and loan term can have outsized effects because the amortization math compounds across many payments. A small change in rate can materially change the monthly principal & interest payment and the model’s total interest over the term.

Input changed What tends to move most What stays the same in the model
Higher interest rate P&I monthly amount and total interest Home price, down payment, add-ons (unless changed)
Longer term Lower P&I monthly (often), higher total interest Loan amount and add-ons (unless changed)
Higher down payment Lower loan amount, lower P&I Rate, term, add-ons (unless changed)

The table is conceptual. The calculator computes specific outputs from your inputs.

Rate sensitivity: a “small” rate change can still be meaningful because it applies to every month of the amortization schedule.
Term trade-off: term affects both monthly payment size and total interest in the model; the direction of each is often different.

Common Modeling Mistakes to Avoid

  • Double-counting taxes or insurance: if you enter annual and monthly versions, the tool prioritizes explicit monthly fields to avoid duplication.
  • Mixing “payment” and “total cost”: the monthly figure is a cash-flow estimate; total interest is a separate amortization-based estimate.
  • Assuming escrow is fixed forever: real tax and insurance costs can change over time; the calculator is a snapshot based on the inputs.
  • Treating outputs as guarantees: the tool is math from your inputs, not an agreement, quote, or lender offer.
Reminder: this page is educational. Use it to understand the mechanics and compare scenarios, not as personal financial advice.

Related Resources

Useful next reads and tools for scenario comparison and learning.

Mortgage Calculator FAQ

Does this calculator store my data?

No. The calculator runs locally in your browser. Inputs are not collected for signups and are not stored by FinFormulas.

Is the result exact?

No. Results are estimates based on your inputs and simplified assumptions. Real payments can differ due to loan program rules, escrow practices, insurance and tax changes, lender fees, rounding, and timing.

What is included in the monthly payment?

This tool estimates principal & interest plus optional property taxes, homeowners insurance, HOA dues, and optional PMI (if entered).

Will this tell me what home I can afford?

No. This tool provides arithmetic outputs from your inputs for scenario comparison. It does not provide individualized guidance or recommendations.

Reviewed & Updated

Calculator logic and on-page content reviewed for clarity and educational accuracy. Last review: December 2025.