Calculate your monthly mortgage payment (PITI), see the full amortization schedule, and model the impact of extra principal payments.
Inputs include home price, down payment (dollar or percent, two-way synced), term (15/20/30 year), APR, property tax, home insurance, HOA, and PMI rate. Tracks PMI drop-off automatically when LTV reaches 78%. Shows total monthly payment, interest paid over the life of the loan, payoff date, and a month-by-month amortization table.
Disclaimer: This is an estimate. Actual mortgage offers depend on credit score, debt-to-income ratio, loan type (conventional, FHA, VA), and lender fees. Always compare offers.
Calculator information
📋 How to use this calculator
- Enter home price, e.g. $400,000.
- Enter down payment in dollars or as a percentage (toggle); US convention is 20% to avoid PMI.
- Choose loan term (15, 20, or 30 years) and APR; typical 30-year fixed in the US is around 6-7% (2026).
- Add monthly costs: property tax (typically 0.8-1.2% of home value per year in the US), homeowners insurance, HOA, and PMI rate (0.5-1% per year if down payment is under 20%).
- View monthly PITI output (Principal, Interest, Taxes, Insurance); PMI auto-terminates at 78% LTV under the Homeowners Protection Act of 1998.
- Enable extra payments to simulate: an additional $200/month toward principal can cut years off the term.
- Tip: housing expense ratio should be no more than 28% of gross income, total debt-to-income no more than 36% (the 28/36 rule).
🧮 Mortgage Payment and Amortization
M = P * [r * (1 + r)^n] / [(1 + r)^n - 1] ; PITI = M + tax_monthly + insurance_monthly + PMI_monthly
- M = monthly principal + interest payment
- P = loan principal (home price - down payment)
- r = APR / 12 (monthly rate)
- n = term in months (30 years = 360)
- PMI auto-terminates at 78% LTV (HPA 1998) or can be requested for cancellation at 80% LTV
For each monthly payment i: interest_i = balance_i * r, principal_i = M - interest_i. Balance decreases monotonically; early on most of M is interest, near the end most is principal.
💡 Worked example: $320,000 mortgage, 30 years, 6.5% APR
Given:- Home price: $400,000
- Down payment: $80,000 (20%)
- Loan principal P: $320,000
- APR: 6.5%
- Term: 30 years (360 months)
Steps:- r = 0.065 / 12 = 0.005417.
- (1 + r)^n = (1.005417)^360 = 7.0286.
- Numerator: 0.005417 * 7.0286 = 0.038076.
- Denominator: 7.0286 - 1 = 6.0286.
- M = 320,000 * (0.038076 / 6.0286) = 320,000 * 0.006317 = $2,021.37 per month.
- Total interest over loan life: (2,021.37 * 360) - 320,000 = 727,694 - 320,000 = $407,694.
Result: P&I payment of $2,021/month; total paid $727,694; total interest $407,694 (127% of principal).
❓ Frequently asked questions
What is PMI and when can it be removed?
PMI (Private Mortgage Insurance) is required when the down payment is less than 20% on a conventional loan in the US, costing 0.5-1.5% of principal per year. The Homeowners Protection Act of 1998 requires lenders to auto-cancel PMI when LTV reaches 78% based on the original amortization schedule. Borrowers can also request manual cancellation at 80% LTV if an appraisal supports the home's value.
What is the 28/36 rule for mortgage affordability?
A US banking rule of thumb: housing expense (PITI) should not exceed 28% of gross monthly income, and total debt (PITI + other debts) should not exceed 36%. Lenders may stretch to 43% (the qualified-mortgage rule under the CFPB ATR/QM standard) but going above 36% increases default risk. The FHA allows up to 31/43, and VA loans use a residual income test instead.
What's the difference between APR and interest rate?
The interest rate is the pure rate used to calculate interest on the loan balance. APR (Annual Percentage Rate) includes the interest rate plus loan fees (origination, discount points, mortgage insurance) expressed annually. APR is always equal to or higher than the interest rate; use APR to compare lenders on an apples-to-apples basis. The Truth in Lending Act (Regulation Z) requires APR disclosure in the US.
Is paying extra toward principal always worthwhile?
Mathematically it saves total interest, but consider opportunity cost: if your expected return on other investments (stocks, index funds) exceeds your after-tax mortgage APR, investing may be more optimal. Confirm no prepayment penalty exists (rare in modern US conventional loans, but possible on older or non-QM loans). Read your note's prepayment clause carefully.
How do I estimate true cost of homeownership?
Beyond PITI, add: maintenance (rule of thumb 1% of home value per year), utilities, HOA if applicable, and closing costs upfront (2-5% of principal). Total true cost of homeownership typically runs 30-40% more than the mortgage payment alone. Don't forget property taxes can rise annually with assessment increases (some states like California cap rises under Prop 13).
📚 Sources & references
Last updated: May 11, 2026