Kaeseru Loan Payoff Calc
Rate stress test, ad-free
$0.99 · Designed for iPad. Not verified for macOS.
How much does the payment rise if the rate goes up 1%? How much interest disappears if you prepay? Answered in yen, not charts. Both prepayment types side by side.
"If the rate goes up 1%, how much more do I pay every month?"
"If I prepay a lump sum, how much interest do I actually save?"
Kaeseru answers those questions in money, not in vague charts.
It shows the difference between doing it and not doing it.
PREPAYMENT, SETTLED IN NUMBERS
Pick when and how much you prepay. Kaeseru leads with the answer:
how much interest you save, and how many months earlier you finish.
It runs both strategies at once - shorten the term vs. lower the payment -
so you can see which one wins, after the prepayment fee.
SEE THE RATE HIKE BEFORE IT HAPPENS
+0.5%, +1.0%, +2.0%, plus any increase you choose.
Up to four scenarios at once, each showing how much your monthly payment grows.
The 5-year rule and the 125% cap common to Japanese variable-rate loans can be
switched on or off, and Kaeseru shows what they hide:
deferred interest, and the balance that gets pushed to the final payment.
REAL APR, FEES INCLUDED
Add origination fees, guarantee fees and monthly insurance,
and you get the effective annual rate instead of the headline rate -
the number you need to compare against car loans and personal loans.
SOLVE FOR ANY OF THE FOUR
Monthly payment, borrowing capacity, term, or rate.
Choose one and Kaeseru solves it from the rest -
even with bonus (semi-annual) payments configured.
NOTHING HIDDEN
The formulas, the monthly rate, how bonus payments are calculated separately -
all visible in the app. Rounding of fractional yen is yours to choose
(down, nearest, or up), so you can reconcile with your lender's schedule.
ALSO
- Terms up to 50 years (600 payments)
- Equal-payment and equal-principal methods
- Bonus payment months you choose yourself
- Amortization schedule by month or year, exportable as CSV
- Save plans and compare any two side by side
WHAT THIS APP DOES NOT DO
- No ads (no ad SDK is bundled)
- No in-app purchases
- No data collection (everything stays on your device)
- No network requests (only opening a link launches your browser)
One purchase. Every feature, from the moment you open it.
Results are estimates. Actual terms and payments depend on your lender's
calculation method. Always confirm with your lender's official schedule.
By Sauna Inc.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
Added a guided first run.
- On first launch you now enter your own loan amount, rate and term as you go. By the time you finish, the result is already calculated for your numbers.
- You can run it again any time from "Show the walkthrough again" in Settings.
- The button for saving a plan was hard to recognise, so the icon changed and the word "Save" was added. You can also save from the bottom of the calculation screen.
The developer, Daisuke Yamaguchi, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Daisuke Yamaguchi
- Size
- 1.7 MB
- Category
- Finance
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - iPad
Requires iPadOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later.
- iPhone
- Languages
- English and Japanese
- Age Rating
4+
- 4+
- Copyright
- © 2026 Sauna Inc.
