How does an extra payment mortgage calculator work?

It first calculates the regular monthly payment for the loan term, then runs a second payoff schedule using that payment plus the extra amount to show payoff time and interest savings.

What does interest saved mean?

Interest saved is the difference between the total interest on the original schedule and the total interest on the schedule with extra monthly payments.

Can I use zero interest?

Yes. If the interest rate is zero, the calculator uses a simple principal divided by months payment.

Quick Tool Labs

Extra Payment Mortgage Calculator

Use this extra payment mortgage calculator to estimate the regular monthly payment, how fast a mortgage may pay off with extra monthly payments, and how much interest might be saved.

Calculator

Loan amount

Annual interest rate (%)

Loan term (years)

Extra monthly payment

Regular monthly payment$0.00

Payoff time with extra0 months

Interest saved$0.00

Enter mortgage details and an extra payment amount to compare payoff speed.

How this extra payment mortgage calculator works

This calculator first estimates the regular monthly mortgage payment for the loan term. It then compares the original amortization schedule with a second schedule that includes the extra monthly payment.

Interest saved = original total interest - total interest with extra payment

It is useful for seeing whether a modest extra payment each month could shorten the payoff timeline or reduce total interest over the life of the mortgage.

Examples

Example 1

On a $300,000 mortgage, adding an extra monthly payment can shorten the payoff schedule and reduce interest.

Example 2

If the interest rate is 0%, the regular payment is simply the loan amount divided by the number of months.

Example 3

A larger extra payment generally lowers payoff time faster and increases total interest savings.

Frequently asked questions

Does this replace an amortization schedule?

No. This is a quick estimate focused on payment, payoff time, and interest savings rather than a full month-by-month table.

What if I do not make extra payments?

Set extra payment to zero and the comparison will match the original loan term and original interest total.

Does this include taxes, insurance, or HOA fees?

No. This tool estimates principal and interest only.