Mortgage Number Lab

Mortgage Calculator

Estimate your total monthly mortgage payment — including principal, interest, taxes, insurance, PMI, and HOA fees.

How This Calculator Works

This calculator estimates your total monthly mortgage payment by combining four components: principal and interest (P&I), monthly property taxes, homeowners insurance, and — where applicable — private mortgage insurance (PMI) and HOA fees.

The principal and interest payment uses the standard amortizing mortgage formula, which calculates a fixed monthly payment that pays down the loan to zero over the chosen term. Enter the loan term in years and months. Common mortgage terms include 15 and 30 years, but the calculator also supports custom remaining terms. Each payment early in the loan goes primarily to interest; as the balance falls, a larger share goes toward principal.

Property taxes, insurance, and HOA fees are not technically part of your mortgage — they are separate obligations. However, lenders typically collect them through an escrow account alongside your mortgage payment, so they appear on your monthly statement.

Mortgage Payment Formula

The monthly principal and interest payment (M) for a standard amortizing mortgage is:

M = P × [r(1+r)^n] / [(1+r)^n − 1]
  • P — Loan amount (principal)
  • r — Monthly interest rate = annual rate ÷ 12 ÷ 100
  • n — Total number of monthly payments (years × 12, plus extra months)
  • M — Monthly P&I payment

For a 0% interest rate, the formula simplifies to M = P ÷ n (equal principal payments, no interest). All calculations use full floating-point precision; values are rounded only for display.

Important Assumptions

  • Payments are fixed monthly payments (standard amortizing loan).
  • Property taxes and insurance are estimated based on your annual inputs and divided by 12.
  • PMI is estimated as a percentage of the loan amount and applies when LTV exceeds 80%. Actual PMI pricing, availability, and cancellation rules vary by lender.
  • The interest rate you enter is the base rate, not the APR. APR includes additional fees not reflected here.
  • HOA fees are fixed and entered as a monthly amount.
  • The calculator does not account for closing costs, points, or origination fees.
  • Taxes and insurance costs change over time; this calculator uses the values you enter as fixed estimates.

Factors That Affect Your Mortgage Payment

Interest rate: Even small rate changes have a significant long-term impact. A 1% rate difference on a $300,000 30-year mortgage changes the monthly P&I by approximately $170 and total interest by over $60,000.
Down payment: A larger down payment reduces the loan amount, lowers monthly payments, may eliminate PMI, and reduces total interest paid. However, it requires more cash upfront.
Loan term: Enter any remaining term in years and months. A 15-year mortgage has higher monthly payments than a 30-year mortgage, but significantly lower total interest. A longer term reduces monthly payments but increases lifetime interest costs.
Property taxes: Property tax rates vary substantially by state, county, and municipality. Some states have effective rates below 0.5% while others exceed 2.5% of assessed value.
Loan type: Conventional, FHA, VA, and USDA loans have different requirements, insurance costs, and eligibility rules. This calculator estimates conventional loan payments.

Frequently Asked Questions

PMI cancellation rights are summarized from Consumer Financial Protection Bureau guidance: How can I cancel PMI?

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Financial Disclaimer: Results are estimates for educational and informational purposes only. They do not constitute financial advice and do not represent a mortgage offer, pre-qualification, or guarantee of approval. Actual payments depend on your lender's specific terms, credit profile, and local market conditions. See our full financial disclaimer and methodology.