How to Calculate Mortgage Monthly Payment (PITI & Amortization) in 2026
When shopping for a home or budgeting for a mortgage, looking only at the advertised Principal and Interest (P&I) rate will cause major financial surprises. The true cost of homeownership in the United States is calculated as PITI: Principal, Interest, Property Taxes, and Homeowners Insurance—plus Private Mortgage Insurance (PMI) and HOA dues where applicable.
This guide breaks down each component of the PITI formula, explains how fixed-rate amortization schedules function, and provides actionable formulas to calculate your exact monthly housing outflow in 2026.
The Total Monthly Housing Equation
Total Monthly Payment = Principal + Interest + Property Tax + Home Insurance + PMI + HOA
1. The Standard Fixed-Rate Amortization Formula
To calculate the monthly Principal & Interest payment (M) on a fixed-rate mortgage, financial institutions utilize the standard annuity amortization formula:
M = P × [ r(1 + r)^n ] / [ (1 + r)^n − 1 ]
- P: Loan Principal (Home purchase price minus down payment)
- r: Monthly Interest Rate (Annual interest rate divided by 12 months)
- n: Total number of monthly payments (360 for a 30-year mortgage, 180 for 15-year)
2. Full Case Study: $450,000 Home with 10% Down at 6.75%
Here is the complete monthly PITI breakdown for a $450,000 median home purchase with a 10% down payment ($45,000), a 30-year fixed loan amount of $405,000 at 6.75% interest, an annual property tax rate of 1.2%, annual insurance of $1,800, and 0.75% annual PMI:
| Payment Component | Calculation Details | Monthly Outflow | % of Total |
|---|---|---|---|
| Principal & Interest (P&I) | $405,000 loan, 6.75% fixed, 360 months | $2,626.83 | 75.1% |
| Property Tax Escrow | ($450,000 × 1.2%) / 12 months | $450.00 | 12.9% |
| Homeowners Insurance | $1,800 annual premium / 12 months | $150.00 | 4.3% |
| Private Mortgage Insurance (PMI) | ($405,000 × 0.75%) / 12 months | $253.13 | 7.2% |
| HOA Maintenance Fee | Community common area assessment | $20.00 | 0.5% |
| Total Monthly PITI Payment | Complete monthly escrow payment | $3,499.96 / mo | 100.0% |