Fixed vs variable mortgage
Initial payment, stress scenarios, certainty, break-even, and risks compared.
Choose variable only if the household can survive a 2–3 point rise without selling; choose fixed for certainty and if you cannot absorb increases.
Key points
- Variable has a lower initial rate but the borrower bears increases.
- Fixed has a higher initial rate but the lender bears specified rate risk.
- Stress-test at +1, +2, and +3 points before choosing variable.
- The break-even depends on how far and fast rates rise.
The core trade-off
A variable rate starts lower, so the initial payment is smaller, but you carry the risk of increases — and Japan left the near-zero era in 2026. A fixed rate (including Flat 35) starts higher, buying certainty because the lender bears the specified rate risk. The right choice is not about predicting rates; it is about whether your household can absorb a rise if you are wrong.
The decision rule
Model the payment at the offered rate plus 1, 2, and 3 points. If the household survives the +2 to +3 stress without selling — with stressed housing costs still a prudent share of net income — variable can make sense and its lower cost may win. If it cannot, choose fixed and treat the higher rate as the price of sleeping at night. Certainty has real value for a single-income household, a tight budget, or anyone who could not sell quickly in a downturn.
Key points to carry away: Variable has a lower initial rate but the borrower bears increases; Fixed has a higher initial rate but the lender bears specified rate risk; Stress-test at +1, +2, and +3 points before choosing variable; The break-even depends on how far and fast rates rise. Use the linked guides and calculators for the full decision, and confirm anything material with the lender, a licensed broker, a judicial scrivener, or a tax accountant before you act.
Who this is for
- Buyers weighing this specific decision
What this is not
- A one-size-fits-all recommendation
- A loan you can afford only at the initial variable rate is a loan you cannot safely afford.
Frequently asked questions
Fixed or floating mortgage rate in Japan — which is better?
There is no universal answer. Floating rates (変動) have been lower and reduce early payments but can rise, increasing your payment later. Fixed rates (固定, including Flat 35) cost more now but lock certainty for the term, protecting you if rates rise. Choose based on how much payment-increase risk you can absorb: if a rate rise would strain your budget, the certainty of fixed can be worth the premium. Model both before deciding.
Are variable rates risky?
Yes, especially when affordability depends on the starting rate. Choose variable only if you survive a 2–3 point rise without selling.
Is a fixed rate risk-free?
No. It removes specified interest-rate risk, not income, property, inflation, or life risk.