Mortgage calculator: monthly payment, rate, and term

Q: What is an amortization schedule and why should I look at one?

It's a month by month table showing how each payment is divided between interest and principal. In the early years of a 30 year loan, the majority of each payment goes to interest rather than reducing what you owe — seeing that breakdown often motivates borrowers to make extra payments or choose a shorter term.

A home loan’s monthly payment depends on the loan amount, annual interest rate , and term years . Small changes in rate or term can noticeably change affordability and total interest paid.

Why a mortgage calculator matters

A home loan’s monthly payment depends on the loan amount, annual interest rate, and term (years). Small changes in rate or term can noticeably change affordability and total interest paid.

What to watch

Fixed vs. adjustable rates and how they affect long-term risk.
Taxes, insurance, and HOA fees are often separate from “P&I” payment.
Extra principal payments can shorten the loan and reduce total interest.

Try the tool

Use the AllMetrics mortgage calculator to plug in price, down payment, rate, and term. It’s a quick way to compare what-if scenarios before you talk to a lender.

Takeaway

Payment = function of principal, rate, and amortization schedule.
Always confirm APR, fees, and PMI rules with your bank.
Run numbers anytime on our mortgage calculator page.

Frequently Asked Questions

What does a mortgage calculator actually compute?

At its core, it applies the standard amortization formula to your loan amount, interest rate, and term to produce a monthly principal-and-interest (P&I) figure. Every payment is split between reducing the balance and covering interest, and the calculator shows exactly how that split shifts over time.

How does the down payment percentage change my monthly bill?

A larger down payment shrinks the loan principal directly, so your monthly P&I drops. It can also push your loan-to-value ratio below 80%, which typically eliminates private mortgage insurance — a cost that can add $100–$200 a month on a mid-sized loan.

Is the number I see the full amount I'll owe each month?

Usually not. The figure from a basic calculator covers principal and interest only. Property taxes, homeowner's insurance, and any HOA dues are billed separately — or rolled into an escrow account by your lender — and can add several hundred dollars on top.

Why does a 30-year loan cost so much more in total interest than a 15-year loan?

You're borrowing the money for twice as long, so interest accumulates on a higher remaining balance for more months. On a $300,000 loan at 6.5%, the difference in lifetime interest between a 15- and 30-year term can easily exceed $150,000 — even though the rate is identical.

What happens if I make one extra principal payment per year?

That single extra payment chips away at the balance faster than the schedule expects, which reduces the interest charged in every subsequent month. On a 30-year mortgage, one extra payment annually can shorten the loan by roughly four to six years, depending on the rate.

How much does a 0.5% rate difference really matter?

More than most people expect. On a $350,000 loan over 30 years, half a percentage point shifts the monthly payment by roughly $100 and the total interest paid by around $35,000. Shopping lenders for even a quarter-point improvement is worth the effort.

Should I choose a fixed or adjustable rate?

Fixed rates lock in predictability — your P&I never changes regardless of market moves. Adjustable rates (ARMs) often start lower but reset periodically, which can push payments up sharply if rates rise. If you plan to sell or refinance within five to seven years, an ARM's initial period might work in your favor; otherwise, fixed tends to be the safer choice.

What is an amortization schedule and why should I look at one?

It's a month-by-month table showing how each payment is divided between interest and principal. In the early years of a 30-year loan, the majority of each payment goes to interest rather than reducing what you owe — seeing that breakdown often motivates borrowers to make extra payments or choose a shorter term.

Can I use the calculator to figure out how much house I can afford?

Yes, but work backwards: start with a monthly payment you're comfortable with, then adjust the loan amount until the output matches. Keep in mind that lenders typically want your total housing costs to stay below 28–31% of your gross monthly income, so use that as a sanity check alongside the calculator.

Does my credit score affect the numbers I should enter?

Your credit score doesn't change the math, but it heavily influences the rate a lender will actually offer you. Someone with a 760 score might qualify for 6.4% while someone at 680 gets quoted 7.1% on the same loan — that gap translates directly into a higher monthly payment and tens of thousands more in total interest.

What is PMI and when does it go away?

Private mortgage insurance protects the lender if you default, and it's typically required when your down payment is below 20%. Once your loan balance drops to 80% of the home's original value — either through payments or appreciation — you can request cancellation. Federal law requires lenders to drop it automatically at 78%.

How do points work, and should I pay them?

One discount point equals 1% of the loan amount paid upfront to lower your interest rate, usually by around 0.25%. Whether it's worth it depends on your break-even timeline: divide the upfront cost by the monthly savings. If you'll stay in the home past that break-even point, paying points makes financial sense.

What's the difference between interest rate and APR?

The interest rate is the base cost of borrowing. APR (annual percentage rate) folds in lender fees, origination charges, and certain other costs, expressing the true yearly cost as a single percentage. When comparing loan offers, APR gives a more honest apples-to-apples picture than the headline rate alone.

How does refinancing affect my mortgage calculation?

Refinancing replaces your existing loan with a new one — ideally at a lower rate or shorter term. The calculator treats it like any new loan, so enter your remaining balance as the loan amount and the new rate and term. Don't forget to factor in closing costs, which typically run 2–5% of the loan amount, when deciding if refinancing pencils out.

Is it better to put more money down or invest the extra cash elsewhere?

This is genuinely a judgment call that depends on your mortgage rate versus expected investment returns, your risk tolerance, and your liquidity needs. A higher down payment guarantees a lower interest cost; investing the difference might yield more over time but carries market risk. Running both scenarios through the calculator — and comparing the interest saved against potential investment growth — gives you a concrete starting point for that decision.