Formula and method
This calculator uses the values you enter and applies the calculation immediately in your browser. The main output formulas are:
- Loan amount:
homePrice<down ? NaN : homePrice-down - Monthly principal and interest:
(() => { if(homePrice<down) return NaN; const principal=homePrice-down; const r=rate/1200; const n=years*12; if (r===0) return principal/n; const pow=Math.pow(1+r,n); return !Number.isFinite(pow) ? principal*r : (principal*r*pow)/(pow-1); })()
Some formulas are undefined for certain input combinations, such as division by zero, equal x-values in a slope calculation, or logarithms of non-positive numbers. In those cases the live tool reports that the result is undefined instead of displaying Infinity or NaN.
Examples
- Example: with Home price = 400000 $, Down payment = 80000 $, APR = 6.5 %, Term = 30 years, this calculator returns Loan amount = 320000 $, Monthly principal and interest = 2022.62 $.
- Share this page with a clean URL: https://specwhale.com/tools/mortgage-calculator/
- Try related finance tools when your next step needs another conversion or calculation.
What this number does and doesn't include
This calculator computes principal and interest based on loan amount, rate, and term -- the core of your monthly payment. It does not automatically include property tax, homeowners insurance, PMI, or HOA fees, which are commonly bundled into an actual mortgage servicer's monthly bill (often called PITI: principal, interest, tax, insurance).
If you're comparing this estimate to a lender's quote and the numbers don't match, that gap is almost always one of those additional line items, not a calculation error -- add your local property tax rate and insurance estimate on top of this result for a more realistic total monthly cost.
Embed this tool
Paste this snippet into your own site or blog post to embed a live, working copy of this tool. It links back to the full page on SpecWhale.
Frequently asked questions
Is Mortgage Calculator free to use?
Yes. Mortgage Calculator is completely free, has no usage limit, and does not require an account, email, or API key.
Does Mortgage Calculator store or upload my data?
No. Mortgage Calculator calculates everything locally in your browser. Nothing you type is sent to a server or stored by SpecWhale.
How accurate is Mortgage Calculator?
Mortgage Calculator uses a standard formula (see the Method section above for the exact expression). For high-stakes financial, medical, or legal decisions, confirm the result with a professional or an authoritative source before relying on it.
Can I embed Mortgage Calculator on my own website?
Yes. Use the "Embed this tool" snippet on this page to add a free, working copy of Mortgage Calculator to your own blog post or page.
SEO and sharing notes
This page has a single clean canonical URL, descriptive metadata, breadcrumb structured data, and internal links to related tools. Supported calculators and converters can also copy a prefilled share link without changing the canonical index URL.