Mortgage Calculator
Work out the monthly payment on a home loan, and how much of it is interest.
Your figures
Result
How to use this tool
- Enter your figures in the fields on the left.
- Results update instantly as you type — there is no button to press.
- Change any input to see how sensitive the answer is to it.
This calculates principal and interest only. Your actual monthly housing cost also includes property tax, homeowners insurance, and often HOA fees or mortgage insurance — together these commonly add 20–30% on top of the figure shown here.
How it works
The calculation runs in your browser as you type — there is no submit button and nothing is sent anywhere. Change any figure and the results update immediately, which makes it easy to see how sensitive the answer is to each input.
Every formula used here is standard and documented in the questions below. Where a result depends on an assumption, the assumption is stated rather than buried.
Frequently asked questions
Does this include taxes and insurance?
No. It shows principal and interest only. Property tax, homeowners insurance, PMI and HOA dues are additional, and together they often add 20–30% to the monthly figure.
How much difference does the interest rate make?
A great deal over 30 years. On a $350,000 loan, moving from 6.5% to 7.5% adds roughly $230 a month and around $84,000 across the full term. It is usually worth more than negotiating the purchase price by a similar amount.
Should I take a 15-year or 30-year term?
A 15-year term has a higher monthly payment but dramatically less total interest — often less than half. Run both here and compare the total repaid figure, not just the monthly one.
Is this calculator free?
Yes, with no account, no limits and no data collection. It runs entirely in your browser.
Should I rely on this for a financial or medical decision?
No. It is a planning estimate built on standard formulas and stated assumptions. For decisions that matter, speak to a qualified professional who can account for your full circumstances.
Is this calculator accurate?
The arithmetic is exact — it uses the standard formula, shown in the questions above. What limits accuracy is the assumptions: the figures you enter, and factors the formula does not model such as fees, taxes and rule changes. Treat the result as a well-founded estimate rather than a quotation.
Do I need to sign up or download anything?
No. It runs in your browser, updates as you type, and stores nothing. There is no account, no download, and no limit on how many times you use it.
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Your files stay on your device. This tool runs entirely in your browser. No file is uploaded, transmitted, or stored. You can verify this by opening your browser's Network tab while using the tool.
Disclaimer. This calculator provides estimates based on standard formulas and the assumptions stated above. It is not financial, medical, tax or legal advice. For decisions that matter, consult a qualified professional. See our full disclaimer.