OraUse the amount actually borrowed
The principal is the loan balance, rather than the whole property price when a down payment is paid separately. A 250,000.00 purchase with a 50,000.00 down payment starts at 200,000.00 borrowed before any financed fees.
The model uses a fixed nominal annual interest rate divided by 12, equal monthly periods and end-of-month payments. Microsoft: constant-payment loan calculations describes the constant-payment method. It does not model an adjustable-rate reset or a mortgage-specific regulatory disclosure.
A 200,000.00 fixed-rate illustration
For 200,000.00 over 30 years at a chosen 6% annual rate, n = 360 and monthly i = 0.005. The unrounded monthly principal-and-interest payment is 1,199.101050… and displays as 1,199.10.
First-month interest is 1,000.00, so 199.10 of that rounded payment reduces principal. Later payments repay more principal as the balance falls. The final payment is adjusted for accumulated cent rounding.
Build a separate housing budget
Property taxes, buildings or homeowners insurance, mortgage insurance, service or association charges, maintenance and utilities can add to the amount you need each month. Their treatment differs by location and loan. Do not read the principal-and-interest result as an approval amount or an affordability decision.
CFPB: principal, interest and amortization distinguishes principal repayment from interest and notes that many U.S. mortgage payments also collect taxes and insurance. Ask what is included in your own quotation.
This principal-and-interest amount is only one part of a housing budget. The interest-rate versus APR guide explains why charges need separate attention, and the loan-comparison calculator makes two stated repayment scenarios easier to inspect.
Compare offers on the same basis
Hold principal and term constant to isolate a rate change. Then compare fees, rate-reset dates and early-repayment terms separately. A lower initial payment on a different type of mortgage is not a like-for-like lifetime-cost comparison.
Common questions
Does this include property taxes or insurance?
The principal-and-interest calculation excludes them. Add verified estimates separately when budgeting for the full housing cost.
Does this predict the rate a lender will offer?
No. You choose the rate. The tool makes no eligibility, underwriting or approval decision.
Can I model a variable-rate mortgage?
A single fixed-rate scenario cannot reproduce rate resets. Compare separate assumptions and use the lender’s product schedule.
Educational estimate using the stated assumptions. Fees, taxes, changing rates and individual circumstances can change an outcome. This is not personalized financial advice. Read the estimates disclaimer.