How much does a 1% rate rise add to my mortgage?

On a large balance, even 1% adds a meaningful amount each month. The exact figure depends on your balance and remaining term, which this calculator works out by comparing repayments at your current and higher rates.

Why stress test for a rate rise?

Rates move over time, and most mortgages re-fix every year or two. Testing how a rise would affect your budget now helps you avoid being caught short when your fixed term ends or floating rates climb.

What can I do to soften a rate rise?

Pay extra while rates are low to reduce the balance, build a buffer, split your loan across terms, or extend the term (which lowers repayments but adds interest). Knowing the impact early gives you time to act.

Interest Rate Rise Impact Calculator

This New Zealand calculator shows how a rise in your mortgage interest rate would change your repayments. Because most loans re-fix every year or two, testing a 1% or 2% rise now helps you avoid a nasty surprise later. You enter your balance, current rate, the rise to test and the remaining term, and the tool shows the new repayment and how much more you would pay each month and year.

Mortgage balance

Current rate

Rate rise to test

Remaining term (years)

extra per month if the rate rises

Current repayment$0

New repayment$0

Extra per year$0

Compares table repayments at your current rate and the higher rate over the remaining term. Banks test new lending against a higher "test rate" for the same reason. Estimate only, not a loan offer.

How it works

The calculator works out the table repayment on your balance at your current rate and at the current rate plus the rise you enter, over the remaining term. The difference is the extra you would pay each month and year if rates climbed that much. It is a simple stress test, the same idea banks use when they check new lending against a higher test rate.

Worked example

On a $550,000 balance over 25 years, a rise from 5.79% to 7.79% lifts the repayment from about $3,475 to $4,164 a month, around $689 more a month, or about $8,270 a year.

Related calculators

Fixed-Rate Rollover Calculator: when a fix ends.
Mortgage Stress Test Calculator: test affordability.
Mortgage Repayment Calculator: repayments.
Borrowing Capacity Calculator: what you can borrow.

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