Mortgage Number Lab

Mortgage Calculator

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

What this calculator estimates

It adds principal and interest to the monthly share of property tax and homeowners insurance you enter, then layers on PMI and HOA when those apply.

Principal and interest use the usual fixed amortizing payment formula. Enter the term in years and months — 15 and 30 years are common, but remaining terms work too. Early payments are mostly interest; later ones shift toward principal as the balance falls.

Taxes, insurance, and HOA are not part of the loan contract. Many lenders still collect them in escrow, so they appear on the same monthly bill.

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

At 0% interest, M = P ÷ n. Math uses full floating-point precision; rounding is for display only. Lenders may round payments or interest differently, so statements can differ by a few cents.

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.

What moves the payment the most

Interest rate: On a $300,000 30-year loan, a 1% rate swing changes monthly P&I by roughly $170 and total interest by more than $60,000.
Down payment: More cash down shrinks the loan, the payment, and often total interest. It can also drop LTV to 80% or below so PMI leaves the estimate — at the cost of more cash at closing.
Loan term: A 15-year schedule usually means a higher monthly payment and far less lifetime interest than 30 years. Longer terms ease the monthly bill and raise total interest.
Property taxes: Effective rates differ widely by state and locality — some areas sit under 0.5% of assessed value; others top 2.5%.
Loan type: Conventional, FHA, VA, and USDA loans use different insurance and eligibility rules. This page models a conventional-style payment estimate.

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.