Mortgage Calculator

What PITI actually means

When most people think “monthly mortgage payment,” they think of principal plus interest. That’s only half the story. Lenders look at PITI — Principal, Interest, Taxes, and Insurance — because it’s the actual amount that has to be paid every month to keep the property. Underestimating PITI is one of the biggest reasons new homeowners feel stretched.

Principal is the portion of each payment that reduces what you owe on the loan. Interest is the lender’s fee for the money — front-loaded so that early payments are almost entirely interest and late payments are mostly principal. Property tax depends on your jurisdiction and the assessed value of the home (typically 0.5-2% per year in the US, varies massively elsewhere). Home insurance covers the structure and your personal belongings against damage and theft.

In the US and Canada, lenders typically require taxes and insurance to be paid through an “escrow” account — your bank collects the monthly amount along with P&I and pays the tax authority and insurance company on your behalf. That’s why your monthly mortgage payment is normally PITI, not just P&I. In other countries (UK, Australia, much of Europe) you pay taxes and insurance separately — but the actual cost of owning is still PITI, however you choose to organize the payments.

Fixed vs variable: which to pick

Mortgages come in two flavors that fundamentally change your risk profile.

Fixed-rate mortgage

The interest rate is locked for the entire loan term. A 30-year fixed at 6.5% will be 6.5% in year 1, year 15, and year 30. Your P&I payment never changes. This is the dominant mortgage type in the US — about 90% of mortgages are 30-year fixed — because Americans value predictability and the US has a robust secondary mortgage market that makes long-term fixed loans economically viable.

Outside the US, fixed-for-30 is rare. UK mortgages typically fix for 2-5 years then revert to a variable rate. Australia and Canada also typically offer shorter fix periods. If you can get a long-term fixed rate at a decent price, lock it in — you’re transferring interest-rate risk to the lender for the life of the loan, which is enormously valuable.

Variable / Adjustable / Tracker mortgage

The rate moves with a benchmark (LIBOR, prime, bank base rate, etc.). When rates fall, your payment drops; when they rise, your payment increases. Some have caps (max increase per period and lifetime). Generally cheaper than fixed at origination, but you’re carrying the interest-rate risk yourself.

Variable mortgages make sense when you expect to move within a few years (less time for rates to spike), when rates are clearly trending down, or when you have enough financial cushion to absorb significant payment increases. They’re risky for first-time buyers who are already stretched at current rates.

Hybrid / ARM (Adjustable-Rate Mortgage)

Fixed for an initial period (commonly 5, 7, or 10 years in the US — written as 5/1, 7/1, 10/1) then adjusts annually. Lower initial rate than 30-year fixed, but the adjustment period creates rate-shock risk if rates rise. Great if you’ll move before the fixed period ends; very risky if you stay through the adjustment.

How much should your down payment be?

The “right” down payment depends on three trade-offs: how much cash you have to deploy, whether you’re trying to avoid mortgage insurance, and what else you’d do with the cash if you didn’t put it into the house.

20% — the classic threshold

In the US, 20% down is the magic number that lets you avoid Private Mortgage Insurance (PMI), which adds 0.5-1.5% of the loan amount per year until you reach 20% equity. On a $320,000 loan, that’s $1,600-4,800/year in PMI. Putting down 20% avoids it entirely. In Australia, the equivalent is Lenders Mortgage Insurance (LMI) avoided at 20%. UK and Canada have similar mortgage insurance requirements for low-down-payment loans.

Less than 20% — when it makes sense

If saving an additional 5-15% would take 2-4 more years, during which home prices keep rising and you keep paying rent, putting down less and accepting mortgage insurance can be financially rational. The math: compare the cost of PMI ($1,600-4,800/year) against the cost of staying out of the market (rent + missed appreciation). In many markets, getting in sooner with PMI beats waiting 3 years for the perfect down payment.

More than 20% — diminishing returns

Putting down 30% or 40% reduces your monthly payment but ties up cash that could be invested elsewhere. If your mortgage rate is 6.5% and you could earn 7-9% in a diversified portfolio, the extra down payment is mathematically inferior. Putting down 50%+ usually means giving up liquidity for emotional rather than financial reasons — which is fine if that’s what you want.

0% down — VA, USDA, and others

Some loan programs (US VA loans for veterans, USDA rural loans, certain first-time buyer programs in various countries) allow 0% down. The math says use them if eligible — getting in with no cash means your savings stay invested. The downside: higher PMI/funding fees, higher total cost, and being fully leveraged means a small price drop puts you underwater.

15-year vs 30-year mortgage

The headline difference is monthly payment. The hidden difference is total interest paid — and the math is shocking.

$320,000 loan at 6.5%:

• 30-year: Monthly P&I = $2,022. Total paid = $727,920. Total interest = $407,920.
• 15-year: Monthly P&I = $2,788. Total paid = $501,840. Total interest = $181,840.

The 15-year costs $766/month more but saves $226,080 in interest over the life of the loan. That’s a 38% reduction in total interest paid for a 38% larger monthly payment. Most financial advisors recommend the 15-year if you can afford it; the interest savings compounds the impact of every other dollar in your financial life.

The 30-year wins in two scenarios. First, if you can’t comfortably afford the 15-year payment without sacrificing retirement contributions or emergency savings — being house-poor is a worse outcome than paying more interest. Second, if you have high-return alternatives for the difference — if you’d save $766/month into an index fund earning 8%, that becomes more than $260,000 in 15 years, larger than the interest savings. Most people don’t actually do this. But it’s a valid argument when the discipline is real.

Mortgage Calculator FAQ

Why is my monthly payment mostly interest at the start?

Because interest is calculated on the remaining balance each month. In month 1 of a $320K loan, you owe $320K, so interest is high (~$1,733 of a $2,022 payment). By month 360, you owe almost nothing, so almost the entire payment goes to principal. This is called amortization. It’s why making extra principal payments early in the loan saves disproportionate amounts of interest — every dollar you knock off the principal in year 1 saves interest for 29 more years.

What’s included in PITI vs not?

PITI covers principal, interest, property tax, and homeowners insurance. NOT included: HOA fees, condo fees, mortgage insurance (PMI/LMI/MIP), utilities, maintenance, repairs, capital improvements, and home warranty premiums. Add 1-2% of home value per year for maintenance budget when estimating true cost of homeownership.

How accurate is this calculator?

The P&I calculation is mathematically exact — it uses the same amortization formula every lender uses. The PITI total is an estimate based on the property tax % and insurance amount you enter. Your actual property tax will depend on local assessor decisions; your insurance premium will depend on the specific property, your credit history, and coverage choices. Get quotes from your jurisdiction and insurer for accurate numbers.

Should I include points or origination fees?

The calculator uses the nominal interest rate, not APR. APR includes upfront fees (points, origination, etc.) amortized over the loan, so it’s slightly higher than the nominal rate. For comparing offers between lenders, use APR. For estimating your monthly payment, use the nominal rate as this calculator does.

What if I want to make extra payments?

This calculator shows the standard amortization. Making extra principal payments shortens the loan and reduces total interest dramatically. A $200/month extra payment on a $320K loan at 6.5% turns a 30-year mortgage into a ~22-year mortgage and saves about $100K in interest. We have a dedicated Lump Sum Repayment Calculator for modeling extra payments precisely.

How is this different from your Loan Calculator?

The Loan Calculator handles any loan generically and shows a full month-by-month amortization schedule. This Mortgage Calculator focuses specifically on home-buying with the PITI breakdown (taxes + insurance), since that’s what mortgage shoppers actually need to budget for. Use whichever framing fits your need.