Estimate annual extra principal created by a recurring extra payment.
UNDERSTAND THE ANSWER
How is this calculated?
This calculator applies the displayed mortgage formula directly to your inputs. It keeps full precision during the calculation and rounds only the displayed result.
Extra Mortgage Payment formulaAnnual extra principal = monthly extra × 12
A practical example
Using the default example values, the calculator substitutes 250 and 12 into the formula. Change the values to model your own scenario.
Calculated result
Extra principal per month
Months paid per year
Calculated answer
$200.00
12
$2,400.00
$250.00
12
$3,000.00
$300.00
12
$3,600.00
Assumptions, interpretation and common mistakes
Calculation assumptions
The values entered for extra principal per month and months paid per year are accurate for the scenario.
Rates and recurring amounts remain constant for the period represented by the formula.
Provider fees, taxes and timing differences are excluded unless they are explicit inputs.
How to interpret the result
Treat the main number as a planning estimate, not a quote, approval or guarantee.
Compare at least a baseline, lower and higher assumption before deciding.
Use the result together with the related mortgage calculators for a broader view.
Common mistakes to avoid
Entering a percentage as a decimal when the field expects a whole percent.
Comparing results that use different time periods or omit different fees.
Rounding inputs early or treating an estimated rate as guaranteed.