Mortgage Calculator: Payment, PMI & Taxes

Mortgage Calculator: P&I, PITI & Amortization

This reference covers fixed-rate P&I from the standard amortization formula, then property tax, insurance, optional PMI, and extras for full housing cost. Worked examples use a $400,000 loan at 6.75% over 30 years unless noted.

What the calculator returns

Fixed-rate P&I from the standard amortization formula, plus monthly tax, insurance, PMI (when applicable), HOA, and any extra principal or biweekly timing you set. Outputs include total interest, payoff date, and a full payment-by-payment schedule.

Worked example:

$400,000 borrowed at 6.75% over 360 months → about $2,594 P&I. On a $500,000 home with 1.2% property tax, add $500/month for taxes; with $200/month for homeowners insurance the all-in PITI lands near $3,294. That scenario assumes 20% down ($100K), so no PMI; under 20% adds another $165-$500/month at typical 0.5-1.5% PMI rates.
What this misses:

Adjustable-rate mortgages, lender-specific PMI cancellation timing, and binding pre-approvals. Property tax and insurance vary widely by county and risk profile; use a lender Loan Estimate for closing numbers. All math runs locally in your browser; treat the results as estimates.
Extras you can model:

Recurring extra principal with a custom start date, up to two dated lump sums, and biweekly half-payments (26 per year, roughly one extra full payment annually).
Where the bigger lever actually is:

A 0.125% rate improvement on a $400K, 30-year loan saves about $33/month. Switching from 30-year to 15-year on the same balance saves roughly $316,000 in total interest (at typical rate spreads). The term decision is usually a bigger lever than a quarter-point of rate negotiation.

How the Monthly Payment Is Calculated

Principal & interest (P&I)

Standard fixed-rate amortization. Monthly P&I:

M = P \times \frac{i(1+i)^n}{(1+i)^n - 1}

where:

P (Principal):

The amount you borrow: home purchase price minus down payment. This is the starting balance that gets paid down over the life of the loan.
i (Monthly interest rate):

Your annual interest rate divided by 12. For example, 6% per year → i = 0.06/12 = 0.005 per month. Interest each month is computed as (current balance) × i.
n (Number of payments):

Total number of monthly payments. A 30-year loan has n = 360; 15-year has n = 180. The formula solves for the fixed payment M that pays off the loan exactly after n months.
What the formula does:

It spreads the loan over n equal payments so that after each payment, the remaining balance is consistent with compound interest. Early on, most of M is interest; later, most of M is principal.

This formula assumes a fixed rate and level payments. Adjustable-rate mortgages (ARMs) use different mechanics and are not modeled here.

Adding Taxes, Insurance, and PMI

The number you see as "Total Monthly" in the calculator is P&I plus the following (all converted to monthly amounts):

Property tax:

Entered as an annual percentage of home value (e.g. 1.2%). The calculator multiplies home price by this rate and divides by 12 for the monthly tax component.
Homeowners insurance:

Entered as an annual dollar amount. Divided by 12 and added to the monthly total.
PMI (Private Mortgage Insurance):

When the down payment is under 20%, enter a monthly PMI amount (typical annual cost is 0.5–1.5% of the loan, divided by 12). The schedule applies PMI until the balance at the start of a payment is at or below 80% of the original home value (simplified; real lenders often use 78% LTV with cancellation rules).
HOA, other costs, and extras:

Any monthly HOA fee, other recurring costs (maintenance, utilities), and optional extra principal payments are added so you see the full impact on payoff date and total interest. Extra payments support a custom start date, and you can model up to two one-time lump sums applied to principal on a specific month.

Understanding Amortization

Why Early Payments Are Mostly Interest

Each month, interest due = (current balance) × (monthly rate). When the balance is largest at the start, most of the payment is interest and only a sliver hits principal. As balance falls, the principal share grows. The balance-over-time chart and schedule table show that curve: shallow early, steeper later.

Crossover Year and Payoff Term

The "crossover year" is the first year in which the total principal paid exceeds the total interest paid. After that, you are building equity faster. "Payoff term" shows how many years until the loan is paid off, it can be shorter than the selected loan term if you make extra principal payments or use biweekly payments (26 half-payments per year, equivalent to one extra full payment per year).

Affordability and alternatives

PITI vs. income, and what else to compare

Lender-approved isn't the same as livable. A $3,294 PITI hits 28% of gross at $141,000/year and 36% at $109,800/year, but neither ratio accounts for childcare, retirement contributions, healthcare premiums, or savings goals that compete for the same paycheck. Run the PITI against your actual budget after those, not just gross income.

28% / 36% / 43% guidelines:

A common front-end (housing-only) cap is 28% of gross income, with a back-end (housing + all other debts) cap around 36% for conservative budgets and up to 43% for what most conventional lenders will approve. The House Affordability Calculator applies the 28/36 framing on the same inputs.
Rent vs. buy:

On a $500,000 home with 20% down, the $100,000 down payment alone, invested at 7% for 10 years, becomes about $197,000. Whether buying still wins depends on home appreciation, the spread between PITI and rent, and how long you actually stay. The Rent vs. Buy Calculator runs the comparison on your specific numbers.
Down payment opportunity cost:

Going from 10% down ($50K) to 20% down ($100K) on a $500K home eliminates PMI (saving $165-$500/month) but ties up an extra $50,000 that could otherwise compound elsewhere. At 7%, $50,000 over 30 years grows to about $381,000, often more than the lifetime PMI savings, but the comparison flips if you value the lower monthly payment or expect lower investment returns.

Mortgage Cost FAQ

What is the monthly payment on a $400,000 mortgage?

At a 6.75% rate over 30 years (close to mid-May 2026 averages), a $400,000 loan runs about $2,594/month for principal and interest. Property tax (typically 0.5-2% of home value annually), homeowners insurance ($150-$300/month for most policies), and PMI if your down payment is under 20% (0.5-1.5% of loan amount per year) sit on top of P&I.

What does a mortgage payment include?

A full mortgage payment typically has four components: principal, interest, property taxes, and homeowners insurance (PITI). If your down payment is under 20%, add a monthly PMI amount in the PMI field; the schedule includes it until the balance reaches 80% of the original home value in this model.

How does interest rate affect my monthly payment?

Rate is the biggest single lever. On a $400,000 30-year loan, the gap between 6% ($2,398/month) and 7% ($2,661/month) is $263/month and roughly $95,000 in total interest over the life of the loan. Even a 0.25% improvement is worth shopping for across at least three lenders, the rate spread between lenders on the same borrower profile is typically 0.25-0.5%.

What is an amortization schedule?

An amortization schedule shows every payment broken into principal and interest over the life of the loan. Early payments are mostly interest; later payments shift heavily toward principal. The schedule lets you see exactly how much equity you build each year.

How much do I need for a down payment?

The conventional minimum is 3–5% for most loan programs, though 20% avoids PMI. FHA loans allow 3.5% down. A larger down payment reduces your loan balance, lowers your monthly payment, and reduces total interest paid; compare scenarios side by side in the tool.

What is PMI and how does it affect my payment?

Private Mortgage Insurance protects the lender if you default, and is typically required when your down payment is below 20%. Enter your estimated monthly PMI in the calculator; typical annual cost is 0.5–1.5% of the loan amount. This tool stops PMI in the schedule when the balance at the start of a payment is at or below 80% of the original home value (a simplified model; many lenders cancel at 78% LTV with a request at 80%).

What is the difference between a 15-year and 30-year mortgage?

A 15-year mortgage typically carries a rate about 0.5% below the 30-year (around 6.25% vs 6.75% in mid-May 2026). On a $400,000 loan that puts the 15-year payment at about $3,430/month versus $2,594/month for the 30-year, $836/month more, in exchange for finishing in half the time and saving roughly $316,000 in interest over the life of the loan ($217,000 total interest on the 15-year vs $534,000 on the 30-year). Pick the 15-year if cash flow comfortably absorbs the higher payment with margin for emergencies and retirement contributions; pick the 30-year if you want lower required payments and the discretion to apply extra principal voluntarily.

How is mortgage interest calculated?

Mortgage interest is calculated monthly on your remaining balance. Each month: remaining balance × (annual rate ÷ 12) = interest due. The rest of your payment reduces principal. As principal falls, the interest portion shrinks, which is why extra payments early in the loan have an outsized impact.

How much house can I afford?

A common guideline is that total housing costs (PITI) should not exceed 28% of gross monthly income, and total debt payments should stay under 43% (the DTI limit most lenders use). Compare your monthly PITI result to gross income for both thresholds before applying.

How do biweekly payments work?

Biweekly means you pay half your monthly P&I every two weeks. That results in 26 half-payments per year, equivalent to 13 full monthly payments instead of 12. The extra payment goes to principal and shortens the loan and reduces total interest. Toggle biweekly in the tool to see updated payoff term and interest savings.

What costs should I include in "Other Monthly Costs"?

Use this field for recurring housing expenses not covered by taxes, insurance, or HOA, such as maintenance (a common rule of thumb is 1% of home value per year), utilities, lawn care, or pest control. Including these gives you a more realistic picture of total monthly housing outlay when comparing to your budget or rent.

Can I model a one-time lump sum payment?

Yes. The calculator supports up to two dated one-time extra payments, useful for modeling a year-end bonus, tax refund, or inheritance applied directly to principal. Enter the amount and select the month and year. The amortization schedule and payoff date will update instantly to reflect the impact.

Mortgage Calculator: P&I, PMI & Tax Analysis

Loan foundation

Escrow & ancillary

Payoff acceleration

Balance Over Time

Amortization schedule

How to use this calculator

Reading your payment breakdown

Example: P&I and PITI

Monthly Payment Split