Mortgage
Calculator
Calculate your monthly mortgage payment, total interest paid, and full amortization schedule. Adjust loan amount, rate, and term to find the right mortgage for you.
| Year | Principal Paid | Interest Paid | Total Paid | Remaining Balance |
|---|
How is my payment calculated?
Your monthly P&I payment uses the standard amortization formula: M = P[r(1+r)^n]/[(1+r)^n−1], where P is the loan amount, r is the monthly interest rate, and n is the total number of payments. Property tax, insurance, and PMI are added on top.
What is PMI?
Private Mortgage Insurance is required by most lenders when your down payment is less than 20% of the home price. It typically costs 0.5–1.5% of the loan amount annually and can be cancelled once you reach 20% equity.
Fixed vs Adjustable Rate
This calculator uses a fixed interest rate. ARMs (Adjustable Rate Mortgages) start lower but can increase after an initial period. Fixed rates provide payment certainty for the full loan term — ideal for long-term homeowners.
The 28% Rule
A common guideline is that your monthly mortgage payment (PITI — principal, interest, taxes, insurance) should not exceed 28% of your gross monthly income. Lenders use this alongside your total debt-to-income ratio to determine affordability.
Sarah and Mike are buying a $400,000 home. They have $80,000 saved for a down payment (20%), good credit, and are choosing between a 15-year and 30-year mortgage at current rates.
| 30-Year Fixed (7.0%) | 15-Year Fixed (6.25%) | |
|---|---|---|
| Loan amount | $320,000 | $320,000 |
| Monthly P&I | $2,129 | $2,743 |
| Monthly difference | — | +$614/mo |
| Total interest paid | $446,440 | $173,740 |
| Interest saved | — | $272,700 |
The 15-year saves $272,700 in interest — but requires $614/mo more. If they invest that $614/mo instead at 7% return for 30 years, they'd accumulate ~$740,000. The math isn't always simple.
Put 20% down if you can
Avoiding PMI (typically 0.5–1.5%/year) saves you money every month and you start with real equity. On a $320k loan, PMI can cost $1,600–$4,800 per year until you hit 20% equity.
Make one extra payment per year
One extra principal payment annually on a 30-year mortgage saves roughly 4–5 years and tens of thousands in interest. The easiest method: pay half your monthly payment every two weeks (biweekly payments).
Improve your credit score first
The difference between a 680 and 760 credit score can be 0.5–1.0% in interest rate. On a $300k loan, that's $30,000–$60,000 over 30 years. Spend 6–12 months improving your score before applying.
Shop at least 3 lenders
Studies show that getting just one extra rate quote saves the average borrower $1,500. Getting five quotes saves over $3,000. Lenders compete — let them. Rate shopping within a 14-day window counts as one credit inquiry.
Get your monthly payment, total interest, and full amortisation schedule in under a minute.