Mortgage Payment Calculator
Calculate the full monthly cost of a mortgage — principal, interest, property tax, insurance, PMI and HOA — not just the principal-and-interest figure lenders advertise.
Mortgage Payment Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Results are a model, not a quotation — an institution's own figures govern.
- Every input is an assumption; change one and the answer changes with it.
- Rounding is applied only at the display layer, so totals may differ by a cent from a statement that rounds each line.
In short: A mortgage payment has four parts, known as PITI: principal, interest, taxes and insurance. On a $420,000 home with 20% down at 6.5% over 30 years, principal and interest is $2,123.75, but the full PITI payment is $2,703.75 once tax, insurance and HOA dues are included.
Formula
P is the amount borrowed, i the monthly rate (annual ÷ 12) and n the number of monthly payments. Only M is fixed by the note; the escrowed items move with assessments.
Worked Example
- Find the loan. $420,000 less 20% ($84,000) leaves $336,000.
- Convert the rate. 6.5% ÷ 12 = 0.541667% per month, over n = 360 payments.
- Apply the annuity formula. P&I = $2,123.75.
- Add carrying costs. Tax $385.00 + insurance $150.00 + HOA $45.00 = $580.00.
- Total the obligation. $2,123.75 + $580.00 = $2,703.75 per month.
Analyst note. P&I is only about 79% of the true payment here. Buyers who budget from an advertised principal-and-interest quote are systematically short by the escrow component, which is exactly the gap that turns an approval into a decline.
Strengths & Limits Of This Model
Where this engine is strong
- Runs entirely in your browser — no figure you type is transmitted or stored.
- Shows the full working, so every number can be traced and challenged.
- Free, unmetered and free of affiliate incentives.
Where it stops
- Generalised assumptions cannot capture every individual circumstance.
- Jurisdiction-specific rules and mid-year changes may not be reflected.
- A model output is not a substitute for a professional review of your position.
Practical Use Cases
Budgeting the real monthly obligation
Lenders advertise principal and interest because it is the smallest defensible number. Adding tax, insurance and dues typically raises it 20 to 25%. Confirm what a lender will approve with the Mortgage Affordability Calculator.
Testing the effect of a larger deposit
Raising the deposit past 20% removes PMI entirely and lowers the balance. Set the down payment below 20% here to see the premium appear, then price it precisely with the PMI Calculator.
Comparing terms before committing
A shorter term raises the payment but cuts total interest sharply. Model each option, then check what voluntary overpayment achieves with the Extra Payment Mortgage Calculator.
Methodology & Editorial Standards
Principal and interest use the standard fixed-rate annuity formula in IEEE-754 double precision. Property tax is applied to the purchase price as a proxy for assessed value, which is accurate at purchase but drifts as assessments are revised. Private mortgage insurance is estimated at 0.55% of the loan annually whenever the deposit is under 20% — a mid-market rate that varies in practice from roughly 0.3% to 1.5% with credit score and loan-to-value. HOA dues and insurance are treated as fixed monthly amounts. Escrowed items are estimates: the servicer recalculates them annually and adjusts the payment accordingly. The engine implements the standard published formula for this calculation. Inputs are validated for domain and sign before evaluation, and any undefined case returns an em-dash rather than a spurious value.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Mortgage Payment Calculator — 20 Expert FAQs
20 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
What does PITI stand for?
Principal, interest, taxes and insurance — the four components of a typical mortgage payment. Principal and interest go to the lender; taxes and insurance are collected into an escrow account and paid on your behalf when they fall due.
Why is my payment higher than the advertised rate suggested?
Because the advertised figure is almost always principal and interest alone. On this example that is $2,123.75, but the true obligation is $2,703.75 once $385.00 of tax, $150.00 of insurance and $45.00 of HOA dues are added.
When do I have to pay PMI?
Whenever your deposit is below 20% of the purchase price on a conventional loan. It typically costs 0.3% to 1.5% of the loan annually. Set the down payment below 20% here and the premium appears in the output automatically.
Can my mortgage payment change if I have a fixed rate?
Yes. The principal and interest portion is fixed, but the escrowed taxes and insurance are not. Reassessments and premium increases flow straight through to your monthly payment, which is why servicers perform an annual escrow analysis.
How much interest will I pay over 30 years?
On $336,000 at 6.5%, total interest is $428,549.48 against total payments of $764,549.48. You pay more in interest than the original loan amount, which is characteristic of any long-dated amortising debt.
Is it better to take a 15-year or 30-year mortgage?
A 15-year term costs far less in total interest but demands a much larger payment that is contractually binding. A 30-year loan with voluntary overpayments reaches a similar destination while preserving the option to stop, which usually suits variable income better.
Does the calculator include closing costs?
No — those are one-off amounts due at settlement rather than part of the monthly payment. They typically run 2 to 5% of the purchase price and should be budgeted separately alongside the deposit.
What property tax rate should I enter?
Use your local effective rate on assessed value; 1.1% is a reasonable national placeholder but rates vary enormously by jurisdiction. Your county assessor publishes the exact figure, and it is worth checking because it is a permanent cost.
Why does a larger down payment help twice?
It reduces the amount borrowed, which lowers principal and interest, and once it reaches 20% it eliminates PMI entirely. The second effect is a pure saving that buys the borrower nothing when it is being paid.
Should I include HOA dues in the payment?
Yes, for budgeting purposes, and lenders include them in the debt-to-income calculation even though they are not paid to the lender. They are a mandatory ongoing cost of the property.
How is the monthly interest rate calculated?
The annual rate is divided by twelve, so 6.5% becomes 0.541667% per month. This simple division is the market convention for US mortgages and differs slightly from a true compounded monthly equivalent.
What happens if I pay half the payment twice a month?
Paid as true biweekly instalments you make 26 half-payments — thirteen full payments — each year, which shortens a 30-year term by roughly four to five years. Confirm your servicer applies them immediately rather than holding them.
Is this mortgage payment calculator free to use?
Yes. It is free, requires no account, and has no usage limits. ApexConverter is funded by contextual advertising, never by selling user data.
Is my data sent to a server?
No. The engine runs as Vanilla JavaScript inside your browser under our Zero-Server Client-Side Execution model. Your figures are computed locally and are never transmitted, logged, or stored.
How accurate is this calculator?
It applies the standard closed-form formula in IEEE-754 double precision, rounding only at the display layer. The engine is reconciled against an independent reference implementation before release.
Does it work on mobile?
Yes. The interface is mobile-first with numeric keypad hints and is tested down to a 320-pixel viewport with no horizontal scrolling.
Can I use it offline?
Largely, yes. Because computation is client-side, the page continues to calculate without a network connection once it has loaded.
Which currency does it use?
Amounts display in US$ accounting format, but the underlying mathematics is currency-agnostic. The result is identical in any currency, so simply read the figures in your own.
Why does a result show an em-dash?
An em-dash indicates the calculation is not defined for the inputs given — typically a division by zero or a value outside the valid domain. We show a dash rather than a misleading number.
How do I report an error?
Email apexconverter.praxiscalc@gmail.com with the tool URL, your exact inputs, the output received and the output you expected. Verified mathematical errors are patched within 72 hours.