Formula guide

Mortgage Calculator formula

The calculator computes fixed-rate principal and interest from the financed amount, adds monthly property tax, homeowners insurance, HOA dues, and estimated PMI when the down payment is below 20%, then simulates the balance month by month when you add extra principal.

How the input values are used

Home price (USD)

The numeric value in USD is used in the calculation; keep units consistent.

Down payment (USD)

The numeric value in USD is used in the calculation; keep units consistent.

Annual interest rate (%)

The numeric value in % is used in the calculation; keep units consistent.

Mortgage term (years)

The numeric value in years is used in the calculation; keep units consistent.

Extra monthly principal (USD)

The numeric value in USD is used in the calculation; keep units consistent.

Annual property tax rate (%)

The numeric value in % is used in the calculation; keep units consistent.

Annual homeowners insurance (USD)

The numeric value in USD is used in the calculation; keep units consistent.

Monthly HOA dues (USD)

The numeric value in USD is used in the calculation; keep units consistent.

Estimated annual PMI rate (%)

The numeric value in % is used in the calculation; keep units consistent.

How to interpret the result

  • The result uses Home price (USD) and Down payment (USD). Change one variable at a time to compare its effect on the outcome.
  • Check whether relevant fees, taxes, and timing assumptions are included before using the estimate.
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