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Mortgage Payment Calculator

PITI, PMI, amortization schedules, and DTI — every number your lender will run, before they run it.

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Mortgage Calculator

PITI payment, amortization, extra payments & DTI

🔄 Your Current Loan

Current Loan Balance ($)

Current Interest Rate (%)

Current Monthly P&I ($)

Months Remaining on Current Loan

Home Value ($) for LTV & PMI

How Long You Plan to Stay

📋 Refinance Type

Rate & term: lower your rate or change the term. Loan amount = current balance + financed closing costs.

✨ New Loan Terms

🏷️ Loan Type

Conventional: min 3% down, PMI if < 20% down, no upfront fees.

🏠 Property

Home Price ($)

Down Payment

Interest Rate (%)

Loan Term

📋 Monthly Cost Factors

Property Tax ($/yr)

Home Insurance ($/yr)

PMI (% of loan/yr)

HOA Fees ($/mo)

💼 Cash to Close

Closing Costs (%) typ. 2–5%

Other Upfront Costs ($) reserves, prepaid

⚡ Extra Principal Payment

Extra Monthly Principal ($)

Gross Monthly Income ($)

Other Monthly Debts ($) car, student, cards

Mortgage Basics

What is PMI and when does it drop off?

PMI (Private Mortgage Insurance) is required for conventional loans with less than 20% down. Under the Homeowners Protection Act, lenders must automatically cancel PMI when your loan balance reaches 78% of the original purchase price (assuming you're current on payments). You can request cancellation at 80% LTV. FHA loans have MIP for the life of the loan (if down < 10%) or 11 years (if down ≥ 10%) — a key reason to refinance into conventional once you have 20% equity.

How much does an extra $100/month save?

On a $280,000 30-year mortgage at 6.8%, an extra $100/month in principal reduces total interest by roughly $38,000 and cuts the loan by about 4.5 years. The savings are larger the earlier you start — extra principal in year 1 stops compounding interest for nearly 30 years. Use the Extra Payment Impact section above to model your exact scenario.

What does a lender count in my DTI?

Front-end DTI = housing PITI ÷ gross monthly income. Conventional loans want this under 28%. Back-end DTI = all monthly debts (housing + car loans + student loans + minimums) ÷ gross income. Conventional programs typically want this under 43%, though some go to 50% with strong compensating factors (large reserves, high credit score). VA has no official DTI cap but has a residual income requirement.

What is the difference between FHA and conventional loans?

FHA loans (backed by the Federal Housing Administration) allow as little as 3.5% down with a 580+ credit score and have flexible qualifying guidelines. The trade-off: upfront MIP of 1.75% of the loan amount plus annual MIP for the life of the loan (or 11 years if down ≥ 10%). Conventional loans require higher credit scores but let you eliminate PMI once you reach 20% equity. VA loans offer 0% down with no PMI for qualifying veterans and active military.

Should I choose a 15 or 30-year mortgage?

A 15-year mortgage builds equity faster and saves tens of thousands in interest, but monthly payments are typically 30–40% higher. A 30-year gives lower required payments and flexibility — you can always pay extra principal when cash flow allows. One strategy: take the 30-year, but pay what a 15-year would cost whenever possible. You keep the lower required payment as a safety net.

Finance Guide

Mortgage Calculator Guide: PITI, Amortization & True Affordability

A practical guide to using a mortgage calculator the way underwriters do — covering PITI, amortization, PMI, escrow, and the debt-to-income ratio that decides whether your loan gets approved.

Written by Calculixy Editorial TeamReviewed by a licensed mortgage professionalUpdated: May 2026

From the Underwriting Desk

Most people use a mortgage calculator to get one number: the monthly payment. But the payment line on a calculator is just principal and interest. What actually hits your bank account every month — and what your lender uses to decide if you qualify — includes property taxes, homeowners insurance, and often mortgage insurance and HOA dues. That full picture is called PITI. Learning to read it is the difference between a payment that fits your life and one that quietly strangles it.

What this calculator does

The Mortgage Calculator estimates your monthly principal-and-interest payment using the home price, down payment, loan term, and interest rate. The deeper view adds taxes, insurance, PMI, and HOA so you see the real PITI number. The tool also reports your total interest paid over the life of the loan and shows how each payment splits between principal and interest as the loan amortizes.

The calculator is most useful as a comparison tool. Running multiple scenarios side by side reveals tradeoffs the headline rate doesn't show. Five basis points on rate, a different loan term, or a $20,000 swing in down payment can shift the math in ways that aren't intuitive without running the arithmetic.

When to use this calculator

Before house hunting, to set a realistic price ceiling based on your real income and debts
When comparing 15-year vs. 30-year terms to see the lifetime interest difference
To see whether a larger down payment is worth it versus keeping cash invested
Before refinancing, to compare current payment vs. new payment and calculate break-even
To estimate how much of each payment goes to principal vs. interest in year one
To stress-test affordability against a hypothetical income loss or rate reset

The mortgage payment formula

Every fixed-rate amortizing mortgage uses the same formula. Whether you're borrowing $80,000 or $800,000, the math is identical — only the inputs change:

M = P × [r(1 + r)ⁿ] / [(1 + r)ⁿ − 1]

Variable definitions

M = Monthly payment (principal and interest only)
P = Principal (loan amount after down payment)
r = Monthly interest rate (annual rate ÷ 12, expressed as a decimal)
n = Total number of payments (loan term in years × 12)

Quick note on PITI: The formula above gives you only the "PI" — principal and interest. To get your full PITI, add monthly property tax (annual tax ÷ 12), monthly homeowners insurance, mortgage insurance if applicable, and HOA dues. PITI is what your lender uses for the qualification ratios.

Step-by-step example

Suppose you buy a $400,000 home, put 10% down ($40,000), and finance $360,000 at 6.5% over 30 years.

P = $360,000
r = 0.065 ÷ 12 = 0.005417
n = 30 × 12 = 360 payments

Plugging into the formula:

M = 360,000 × [0.005417 × (1.005417)^360] / [(1.005417)^360 − 1] M ≈ $2,275 per month

That's the principal-and-interest payment. To get real PITI, add:

Property tax (1.2% of home value annually): $400,000 × 0.012 ÷ 12 = $400/month
Homeowners insurance: roughly $125/month for a $400K home
PMI (down payment under 20%, ~0.65% of loan annually): $360,000 × 0.0065 ÷ 12 = $195/month

Real PITI: $2,995/month. The "principal and interest" calculator number ($2,275) was understated by 32%.

Over 30 years, total interest paid on that loan is roughly $459,000 — more than the original loan amount. That total is the cost of borrowing, and it's the number most calculators hide unless you scroll.

What lenders actually check: debt-to-income (DTI)

A mortgage payment that fits a calculator may not fit an underwriter's worksheet. Lenders use two ratios to decide whether to approve you:

Front-end DTI

Front-end DTI = (Housing PITI ÷ Gross monthly income) × 100

This is the share of your pre-tax income going to housing alone. Most conventional loans want this under 28%. FHA loans allow up to 31%. VA loans are more flexible, often allowing 35%-41%.

Back-end DTI

Back-end DTI = (All monthly debts ÷ Gross monthly income) × 100

This adds your car payment, student loans, minimum credit-card payments, and personal loans to your housing PITI. Conventional loans typically want this under 43%. Some programs flex to 50% with strong compensating factors like high credit scores or significant cash reserves.

If your gross monthly income is $8,000 and you have a $400 car payment and $200 in student loan minimums, your maximum housing PITI under a 43% back-end DTI is: ($8,000 × 0.43) − $400 − $200 = $2,840. Plug that back into the calculator at current rates to see what home price it supports.

The 28/36 rule of thumb: Keep housing PITI under 28% of gross income and total debts under 36%. Lenders may go higher, but household budgets rarely stay healthy beyond it.

How amortization actually works

In the first year of a 30-year mortgage at 6.5%, more than 80% of each payment goes to interest, not principal. The split slowly inverts over the loan term. By year 23, more than half of each payment finally goes to principal. By year 28, nearly all of each payment is principal.

This matters in two ways. First, paying extra toward principal early in the loan saves disproportionately more interest than paying extra later. An extra $200/month for the first five years on a $360,000 mortgage saves more total interest than $200/month for the last fifteen years — even though it's a third of the total extra payments. Second, the equity you build in the first few years from regular payments alone is small. Your equity growth in those early years comes mostly from home appreciation, not principal paydown.

This is also why "biweekly mortgage payment" programs work: paying half your monthly payment every two weeks results in 26 half-payments per year — equivalent to 13 full payments instead of 12. That one extra payment per year, applied to principal, typically shaves four to six years off a 30-year mortgage.

Real-world use cases

1. Comparing 15-year vs. 30-year terms

A 15-year loan has a higher monthly payment but cuts total interest by more than half. On a $360,000 loan at 6.5%, the 30-year costs roughly $459,000 in interest. The 15-year at 6% (15-year rates are typically 0.5%-0.75% lower than 30-year) costs roughly $186,000 in interest — a $273,000 difference. The trade-off: a higher monthly payment locks up cash flow you might want for other goals.

The compromise some borrowers use: take a 30-year mortgage but make extra principal payments equal to what a 15-year payment would be. You get the flexibility of the lower required payment with the same interest savings, as long as you stay disciplined.

2. Should I put more down?

A larger down payment lowers the principal, which lowers the payment and the lifetime interest. It also eliminates PMI once you cross 20%. But putting every available dollar into a down payment leaves you cash-poor. The opportunity cost matters: if your mortgage rate is 6.5% and your savings could earn 7%-8% in a diversified portfolio over the long term, the math on extra down payment versus investing is close. Lower mortgage rates make a bigger down payment less compelling; higher long-term investment returns argue for putting less down. Run the comparison in our Compound Interest Calculator.

A useful frame: the down payment is a guaranteed return equal to your mortgage rate. At 6.5%, every extra dollar of down payment "earns" 6.5% (the interest you no longer pay). That's a strong, risk-free return — but only if you have an adequate emergency fund first.

3. Refinancing decisions

The right refinance question is not "are rates lower now?" It's "how long do I need to stay in the home to recoup the closing costs?" Divide total closing costs by monthly savings:

Break-even months = Total closing costs ÷ Monthly savings

If closing costs are $6,000 and your refinance saves $200/month, break-even is 30 months. If you plan to stay in the home at least three years, refinancing makes sense. If you might move in two years, it doesn't.

4. Stress-testing affordability

Before buying, run the calculator at higher rates and lower income scenarios. If your job became uncertain or rates rose by a point during a future refinance, would the payment still fit? Most buyers run only the optimistic scenario. The pessimistic one is the one that matters.

Common mistakes

Confusing PI with PITI. The headline number on most online mortgage calculators is principal and interest only. Add 20%–35% for the real cost.
Ignoring PMI. If your down payment is under 20%, expect 0.3%–1.5% of the loan amount per year in private mortgage insurance. PMI typically falls off automatically at 78% loan-to-value based on original value.
Forgetting closing costs. Buyers pay 2%–5% of the home price in closing costs at signing. Some can be rolled into the loan; many cannot. A $400,000 home means $8,000-$20,000 in closing costs.
Stretching to the maximum approval. A lender's max DTI is the most they'll lend you, not the most you should borrow. Build in margin for repairs, job changes, kids, healthcare, retirement contributions.
Comparing rate alone instead of APR. APR includes points and lender fees in addition to the interest rate. Two loans at 6.5% can have very different APRs.
Ignoring escrow. Most lenders require escrow for taxes and insurance, which means your payment can rise even with a fixed-rate mortgage when property taxes or insurance premiums go up.
Skipping the amortization schedule. The schedule shows how slowly principal builds in the early years. Reviewing it once changes how you think about paying extra.

Frequently asked questions

What is a good mortgage interest rate?

"Good" is relative to the current market. Track the weekly Freddie Mac Primary Mortgage Market Survey for the running average on 30-year fixed loans, then compare quotes against it. Your personal rate depends on credit score, down payment, debt-to-income, loan type, and property type. Excellent credit (760+) typically gets the published average or lower; 620-680 credit can be 0.5%-1.5% higher.

How much house can I really afford?

A conservative answer: housing PITI no more than 25%–28% of gross monthly income, with a six-month emergency fund still intact after closing. Lenders will approve you for more. Most personal finance experts say not to take it. The most common regret among first-time buyers is buying at the top of their approval range.

Is it better to put 20% down?

Twenty percent eliminates PMI, lowers the monthly payment, and reduces lifetime interest. But it also drains liquidity. If you'd be tapping your emergency fund or shorting your retirement contributions to hit 20%, a smaller down payment with PMI is often the smarter trade. PMI also drops off automatically at 78% LTV, so the cost is temporary.

When does PMI go away?

Federal law (the Homeowners Protection Act) requires PMI to be removed automatically when your loan balance reaches 78% of the original property value (assuming you're current on payments). You can also request removal at 80% LTV based on either the original value or a current appraisal — useful if your home has appreciated.

What's the difference between fixed and adjustable rate mortgages?

Fixed-rate mortgages keep the same rate and payment for the entire term. ARMs start with a lower fixed period (commonly 5, 7, or 10 years), then adjust periodically based on a benchmark index. ARMs make sense if you're confident you'll move or refinance before the adjustment period. They're risky for long-term holders, especially when rates trend upward.

Does the calculator factor in tax deductions?

No. The mortgage interest deduction lowers your effective cost of borrowing if you itemize. Most homeowners take the standard deduction now under current tax law, so the benefit applies to fewer buyers than it used to. Talk to a tax professional for your specific situation.

Should I pay points to lower my rate?

Each point costs 1% of the loan amount and typically lowers the rate by 0.25%. Calculate the break-even: divide the cost of points by the monthly savings. If break-even is shorter than how long you'll keep the loan, paying points wins. If you might refinance or sell soon, it loses.

What if rates drop after I close?

You can refinance. Calculate break-even on the refinance the same way you'd calculate it on any loan — closing costs divided by monthly savings. As a rule of thumb, refinancing becomes worth considering when rates drop by at least 0.75%-1.0% from your current rate, assuming you'll stay in the home long enough to recoup costs.

Related Calculixy calculators

From the editorial desk: The most common mortgage mistake is treating the calculator's payment number as the answer. It's the starting point. The real questions — Can I afford this in a recession? What happens if rates reset? Will I still have an emergency fund after closing? — never appear on the calculator. Answer those first. The calculator gives you the arithmetic. Affordability is judgment.

Calculixy's Mortgage Calculator provides estimates for educational use only and does not constitute a loan offer, financial advice, or a guarantee of approval. Actual rates, payments, and approval depend on your full financial profile, the property, and current lending guidelines. Consult a licensed mortgage professional before making borrowing decisions. All calculations run locally in your browser; Calculixy does not collect or transmit the values you enter.