How is a monthly mortgage payment calculated?

Monthly mortgage payments are calculated using the standard amortization formula: M = P * [r(1+r)^n] / [(1+r)^n - 1], where M is monthly payment, P is principal, r is monthly interest rate, and n is total payments.

What does PITI stand for in a mortgage?

PITI stands for Principal, Interest, Taxes, and Insurance. These are the four core components of a monthly mortgage payment.

How does a larger down payment affect my mortgage?

A larger down payment reduces the principal loan amount you need to borrow. This directly lowers your monthly payment, reduces total interest paid, and can eliminate Private Mortgage Insurance (PMI) if you reach 20% down.

Mortgage & Refinance Planner

Calculate standard monthly payments, model rent-vs-buy scenarios, analyze refinancing benefits, or determine home affordability.

Live

Parameters

R Reset

Presets

Scenario Mode

Analysis Mode

Interest Rate (%)Annual Percentage Rate (APR). US average 30yr mortgage: ~7%.

6.50%

0.10%25.00%

Loan Term (Years)

30 Years

5 Years40 Years

years

Analytics Dashboard

Est. Monthly Payment

$2,522.62Projected · 99%

Good Standing

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Principal & Interest$2,022.62

Monthly Property Tax$400.00

Monthly Insurance$100.00

Financial & Educational Insights

Based on a purchase price of $400,000.00 with a down payment of $80,000.00:

Your net loan principal is $320,000.00.
Over the life of the 30-year loan, you will make 360 payments.
Estimated total outlay (principal + interest) is —, including — in total interest charges.

Optimal Down Payment

Excellent! Your down payment of 20.0% meets the 20% standard. You have successfully avoided PMI monthly overhead.

Prepayment Power Tip

Paying an extra $160/monthdirectly toward principal can shorten your mortgage term by 4–5 years and save you tens of thousands in interest. Toggle the "Extra Monthly Payment" slider under Advanced Options to model this.

Interest Rate Warning

Your interest rate is 6.5%. Refinancing to a rate just 1% lower once market rates cool down will reduce your monthly payment and yield significant lifetime interest savings.

No Prepayment Payoff DelayImprove planning safety margin

Allocate a small monthly prepayment (e.g. 10% extra) to save years of interest drag.

Not scheduling extra prepayments extends debt duration.

High Debt-to-Income (DTI)Improve planning safety margin

Increase down payment to lower the loan balance, opt for a cheaper home, or choose a longer loan term.

Monthly housing payment exceeds 28% of your gross monthly income.

Scenario Analysis Projections

Scenario	Profile	Est. Monthly Payment
Base Settings	Default inputs and growth assumptions	$2,522.62
Conservative	Lower yield, higher inflation, haircuts	$2,682.96
Optimistic	Favorable yield, lower inflation, growth	$2,418.56
Stress Test	Severe economic crash and high inflation	$3,074.79

Educational estimate. Not financial advice. Interest rates and lender policies vary.

InterpretationGood DTI ratio within the CFPB recommended 36% back-end limit. No Prepayment Payoff Delay: Not scheduling extra prepayments extends debt duration. High Debt-to-Income (DTI): Monthly housing payment exceeds 28% of your gross monthly income.

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How to Use the Mortgage & Refinance Planner

Planning to buy a home? Use our free mortgage payment calculator to estimate your total monthly housing costs. Simply input the home purchase price, down payment, annual interest rate, and loan term to calculate your principal and interest payments. Our tool also factors in property taxes and homeowners insurance to give you an accurate picture of your real monthly budget.

Input variables:

Scenario Mode: Bounded parameter in the mathematical model.
Analysis Mode: Bounded parameter in the mathematical model.
Home Price ($): Bounded parameter in the mathematical model.
Down Payment ($): Bounded parameter in the mathematical model.
Interest Rate (%): Bounded parameter in the mathematical model.
Loan Term (Years): Bounded parameter in the mathematical model.
Annual Property Tax ($): Bounded parameter in the mathematical model.
Annual Home Insurance ($): Bounded parameter in the mathematical model.
Extra Monthly Payment ($): Bounded parameter in the mathematical model.
Target Monthly Payment Budget ($): Bounded parameter in the mathematical model.
Down Payment (%): Bounded parameter in the mathematical model.
New Loan Interest Rate (%): Bounded parameter in the mathematical model.
New Loan Term (Years): Bounded parameter in the mathematical model.
Refinance Closing Costs ($): Bounded parameter in the mathematical model.
Initial Monthly Rent ($): Bounded parameter in the mathematical model.
Annual Rent Increase (%): Bounded parameter in the mathematical model.
Annual Renters Insurance ($): Bounded parameter in the mathematical model.
Alternative stock return (%): Bounded parameter in the mathematical model.
Home Appreciation Rate (%): Bounded parameter in the mathematical model.
Annual Maintenance Rate (%): Bounded parameter in the mathematical model.
Annual Inflation Rate (%): Bounded parameter in the mathematical model.
Interest Compounding: Bounded parameter in the mathematical model.
Payment Frequency: Bounded parameter in the mathematical model.
Interest Rate Structure: Bounded parameter in the mathematical model.
Loan Type: Bounded parameter in the mathematical model.
FICO Credit Score: Bounded parameter in the mathematical model.
Gross Annual Income ($): Bounded parameter in the mathematical model.
Other Monthly Debts ($): Bounded parameter in the mathematical model.
Monthly HOA Fees ($): Bounded parameter in the mathematical model.
Liquid Cash Reserves ($): Bounded parameter in the mathematical model.
Discount Points: Bounded parameter in the mathematical model.
Lender Origination Fees ($): Bounded parameter in the mathematical model.
Capitalize Upfront Fees: Bounded parameter in the mathematical model.

How Mortgages Work: Amortization & Principal Math

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Mortgage Worked Example Pack: 5 Real-World Scenarios

Step-by-step mathematical walkthroughs of 30-year fixed, 15-year accelerated, extra prepayment payoff, refinance break-even, and low down payment PMI scenarios.

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Refinance Break-Even Decision Guide: When Does Refinancing Pay Off?

Learn how to calculate your refinance break-even period, evaluate upfront closing costs, avoid loan term reset traps, and decide when to lock a new rate.

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