Kaeseru Loan Payoff Calculator
Mortgage Extra Payment & APR
$0.99 · Designed for iPad. Not verified for macOS.
Fixed or ARM, 15 or 30 years? Compare up to 5 saved loans side by side and see the exact difference in monthly payment, total cost and interest. No ads, no account.
“If the rate goes up 1%, how much more do I pay each month?”
“If I make a $10,000 overpayment, how much interest do I really save?”
Kaeseru answers those questions in money – the exact difference between doing it and not doing it – instead of a vague chart.
■ Extra payments, answered in money
Choose when and how much, and Kaeseru shows first how much interest you save and how many months sooner you are mortgage-free.
It runs both options at once – keep the payment and shorten the term, or keep the term and lower the payment – so you can see which is better. Prepayment fees are subtracted too.
■ Compare up to 5 saved plans side by side (new)
Fixed vs. variable, 25 vs. 30 years, a bigger deposit. Save the scenarios and compare 2–5 of them in one table: monthly payment, rate, APR, term, total cost including fees, total interest, interest share and payoff date. Every plan is shown as a difference from your baseline, and the cheapest plan is marked. Export the table as CSV or share it as text.
■ See a rate rise before it happens
+0.5%, +1.0%, +2.0% and your own worst case, side by side, with the extra monthly cost of each.
■ The real rate including fees (APR)
Add arrangement, broker or valuation fees and Kaeseru calculates the APR, so you can compare offers on equal terms.
■ Solve for any of the four
Monthly payment, loan amount, term or rate – pick one and Kaeseru works it out from the other three.
■ Built for the United States
・US dollars, 30- and 15-year terms and APR out of the box
・Amounts in your currency to the cent, with a choice of rounding (down, half up, up) to match your lender's schedule
・Level payment (annuity) and level principal
・Terms up to 50 years (600 payments)
・Full amortization schedule, monthly or yearly, with CSV export
・Every formula shown on screen, so you can check the numbers
■ What this app never does
・No ads (no ad SDK)
・No in-app purchases or subscriptions – a single one-time purchase unlocks everything
・What you enter never leaves your device. To improve the app, only anonymous usage data (such as which screens are opened) is counted with Google Analytics (you can turn this off in Settings).
Results are estimates. Actual payments depend on your lender's calculation method; always check your lender's official schedule.
Kaeseru is made by Sauna Inc., Tokyo.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
Minor improvements.
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 Linked to You
The following data may be collected but it is not linked to your identity:
- Location
- Identifiers
- Usage Data
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Daisuke Yamaguchi
- Size
- 4.3 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. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
English and 2 more
- English, German, Japanese
- Age Rating
4+
- 4+
- Copyright
- © 2026 Sauna Inc.
