Mortgage Calculator
Thinking about buying a home? Enter price, down payment, rate, and term and you will see your monthly payment and total interest. It makes budgeting much clearer.
TL;DR
- Each monthly payment stays the same, but early payments cover mostly interest
- Amortization Formula: Monthly Payment = P × [ r(1 + r)^n ] ÷ [ (1 + r)^n - 1 ]
- Example 1: Sizing a $300,000 home loan at 4.5% interest over 30 years
How it works
Each monthly payment stays the same, but early payments cover mostly interest. Over time more of your payment reduces the principal.
The math
Convert the annual rate to a monthly rate and apply the amortization formula to get the fixed payment.
P is the principal loan amount, r is the monthly interest rate (annual rate divided by 12 months and 100), and n is the total number of monthly payments (years × 12).
Amortization schedule example: $300,000.00 at 4.5% for 30 years
Monthly payment: $1,520.06. Total interest over the full term: $247,220.13.
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Mortgage: payment, amortization & simulation
For mortgage payment and amortization use French method: Payment = P×[i(1+i)^n]/[(1+i)^n−1]. Example: $200k at 3.5% for 25 years (300 payments) → ~$1,001/mo. Our mortgage amortization calculator shows full schedule instantly.
Examples
Example 1: Sizing a $300,000 home loan at 4.5% interest over 30 years
- Principal (P): $300,000
- Monthly Interest (r): 4.5% ÷ 12 ÷ 100 = 0.00375
- Total Months (n): 30 × 12 = 360
- Calculate Payment: $300,000 × [0.00375(1.00375)^360] ÷ [(1.00375)^360 - 1] = $1,520.06 per month
- Total Paid over life of loan: $547,221.60 (Interest cost: $247,221.60)
When to use it
✦ Home Affordability Evaluation
Verify if a specific real estate purchase aligns with the standard 28/36 debt-to-income rule.
✦ Loan Refinancing Comparisons
Assess if refinancing to a lower interest rate covers the associated closing transaction costs.
✦ Extra Principal Payment Strategies
Calculate how making one extra payment per year reduces the total lifespan of your mortgage debt.
⚠ Common mistakes
- Ignoring Closing Costs and Property Taxes: Looking only at the base principal and interest, ignoring HOA fees, property insurance, and municipal taxes.
- Over-borrowing: Selecting the maximum loan size approved by the bank rather than what matches your personal disposable income.
FAQ (6)
What is principal vs interest?
Principal is the money borrowed; interest is the bank's fee for lending you that money.
Does a 15-year term save money compared to a 30-year term?
Yes, because the loan has a shorter duration, you accrue far less interest, saving tens of thousands of dollars.
If I type my salary or prices here, do you store them?
No — and that's deliberate. Everything runs locally in your browser, nothing leaves your device. We don't see your net salary, your margins, or the VAT numbers you test. For a finance tool that matters: you can run a quick check on a payslip or an invoice while on public Wi-Fi and close the tab knowing no trace is kept server-side.
Can I use it on the train without signal to check an invoice?
Yes. Load the page once, then it works offline. VAT, discount and mortgage math are all pure JavaScript — no API call. I often test it in airplane mode: open the mortgage page, type 250,000 at 4.5% for 25 years, you get the schedule instantly, even in a tunnel.
Can I file taxes with these results?
Use it as a fast sanity check, not as the final filing. Formulas are standard (e.g. Net = Gross / 1+VAT) and verified against official sources listed at the bottom, but rates and thresholds change — Italy's 22% vs Germany's 19%, or IRPEF brackets. For the actual declaration, double-check with your accountant or Agenzia delle Entrate / HMRC / IRS.
How do I send a calculation to my accountant?
Hit 'Share Link' under the results. It encodes the inputs in the URL — e.g. ?price=1200&vat=22 — so your accountant opens the exact same view, no screenshot needed. You can also copy the result with one tap and paste it into an email.
Sources & References
⚠ Financial Disclaimer
This tool provides estimates for informational purposes only and does not constitute financial, tax, or legal advice. Results may vary based on local regulations, rates, and individual circumstances. Always consult a qualified professional before making financial decisions.