Mortgage interest rates are rising! How much more will people with a 30 million yen loan have to pay each month?
In October 2026, mortgage interest rates are once again in the spotlight.
Following the Bank of Japan’s interest rate hike, some banks have raised their variable interest rates.
However, what people are concerned about is not the complex talk of monetary policy, but rather,
“In the end, how much will my mortgage payment increase?”
isn’t that the question?
In this article, we will look at the numbers to see what actually happens.
1. What happens if interest rates rise by 0.25%?
For example, let’s consider someone with a mortgage balance of 30 million yen.
Suppose the interest rate rises from 1.00% per year to 1.25% per year.
The difference in interest rates is only 0.25 percentage points.
At first glance, it might not feel like a very large amount.
However, because the amount borrowed for a mortgage is large, even a small change in interest rates has an impact.
A simple calculation of the interest rate increase on a 30 million yen balance is:
30 million yen × 0.25% = 75,000 yen per year
In monthly terms,
this is equivalent to an increase in interest burden of approximately 6,250 yen.
*This is an estimate assuming the balance does not change. In reality, the principal decreases through repayment, so the annual interest increase will differ.
2. Does the monthly repayment amount increase immediately?
Actually, there is a point to note here.
Variable rate mortgages have a “5-year rule” depending on the bank and the contract.
This is a mechanism where the monthly repayment amount does not change for a certain period even if interest rates rise.
However, even if the repayment amount does not change, the proportion of interest paid will increase.
In other words,
even if the monthly repayment amount remains the same, there is a possibility that the mortgage principal will become harder to reduce
.
If you are unaware of this mechanism, you might be surprised when the repayment burden increases later on.
From here on, we will specifically compare the impact of interest rate hikes based on the outstanding loan balance.