Guides JP

Mortgage Calculator

Calculate monthly payments, total cost, and interest in real-time. Compare repayment methods, simulate prepayments, auto-calculate tax deductions, and view repayment charts all in one page.

Last updated: 2026/10/16 Finance Feedback & bug reports
JPY
%
Rate Presets
yrs
JPY

Switch the repayment method between Equal Installment and Equal Principal, or use Compare Both to view total payment and total interest side by side. The yearly repayment table also shows the principal/interest/balance breakdown for each year (all figures are estimates).

Mortgage Tax Deduction
Apply deduction
Repayment Chart
Yearly Repayment Table

Results are estimates and may differ from actual loan terms.

Calculations assume a fixed interest rate. Variable rates may change payments.

The mortgage deduction follows the rules for move-in in 2025 or 2026 (new or existing, housing type, and the child-rearing/young-couple extra) and is limited to the income and resident tax calculated from your salary. Other conditions apply, such as floor area (50 m2 or more; 40-50 m2 only in years with total income of 10 million JPY or less). Confirm actual amounts with the tax office or your municipality (based on National Tax Agency No.1211-1 and No.1211-3 and Ministry of Internal Affairs materials as of October 2026).

Bonus payments assume twice per year (June and December).

This tool is for general information and estimation only and is not a solicitation or advice to purchase any financial product. Consult a financial institution or professional before signing a contract.

Mortgage deduction sources (as of October 2026, Japanese): National Tax Agency No.1211-1 (new homes) / National Tax Agency No.1211-3 (existing homes) / Ministry of Internal Affairs: resident tax changes (notice) / National Tax Agency No.1199: basic deduction / National Tax Agency No.1410: employment income deduction

JPY
years later
Prepayment Effect
Repayment Chart

To compare prepayment scenarios in more detail, also try our dedicatedPrepayment Simulator.

Results are estimates and may differ from actual loan terms.

Calculations assume a fixed interest rate. Variable rates may change payments.

This tool is for general information and estimation only and is not a solicitation or advice to purchase any financial product. Consult a financial institution or professional before signing a contract.

JPY/mo
%
yrs
JPY
Borrowing Capacity
Debt-to-Income Ratio

Results are estimates and may differ from actual loan terms.

Calculations assume a fixed interest rate. Variable rates may change payments.

How to Use

1

Enter Loan Conditions

Set loan amount, interest rate, and period. Compare equal installment vs equal principal methods.

2

Set Prepayment & Deductions

Optionally add prepayment timing/amount and mortgage deduction settings (move-in year, new or existing, housing type, salary).

3

Review Results

Check monthly payments, total costs, and interest via charts and tables. Adjust conditions to simulate.

About Mortgage Calculator

A comprehensive tool for calculating mortgage payments, prepayment effects, and tax deductions. Compare equal installment and equal principal methods, factor in bonus payments, and view detailed repayment schedules all in one page.

Features

  • Repayment Method ComparisonCompare equal installment vs equal principal in real-time.
  • Prepayment SimulationSee exact savings from term reduction or payment reduction.
  • Tax Deduction SupportCovers the rules for move-in in 2025 and 2026 (new or existing, housing type, child-rearing extra) and caps the deduction at the tax calculated from your salary.
  • Repayment ChartVisualize principal/interest breakdown and balance over time.

Use Cases

  • Planning to purchase a home
  • Comparing repayment methods
  • Finding optimal prepayment timing
  • Estimating tax deduction benefits
  • Reverse-calculating borrowing capacity from income

Related Tools & Guides

For your home-purchase financial plan, also try these tools and explainer articles (all amounts are estimates).

FAQ

What is the difference between equal installment and equal principal?
Equal installment keeps monthly payments constant (principal + interest), making budgeting easier. Equal principal keeps the principal portion constant while interest decreases over time, resulting in higher initial payments but lower total interest.
How much is the mortgage tax deduction?
0.7% of the year-end loan balance is deducted from your income tax (and any remainder from resident tax). The loan limit and period depend on the move-in year, new or existing, and housing type. For a new build moved into in 2026: certified 45 million JPY, ZEH-level 35 million, energy-standard 20 million (50, 45 and 30 million for child-rearing or young-couple households) for 13 years, while "Other" is generally not eligible. Existing homes: certified and ZEH-level 35 million and energy-standard 20 million for 13 years, and "Other" 20 million for 10 years. However, you can only deduct up to that year's income tax plus a resident tax cap (5% of income tax taxable income, up to 97,500 JPY), so depending on your income the full 0.7% may not be usable (for example, about 112,000 JPY a year for a single person earning 4 million JPY).
Should I prepay during the tax deduction period?
Since deductions are based on year-end balance, prepaying during the deduction period can reduce your deduction. If your deduction is already capped by your tax, a slightly lower balance may not change it. It may be better to prepay after the deduction period ends. Use this tool to compare both scenarios.
Variable or fixed rate - which should I choose?
Variable rates start lower but carry rate-increase risk. Fixed rates provide payment certainty but start higher. Use this tool to simulate different rates and compare.
What are the pros and cons of bonus payments?
Pros: lower monthly payments. Cons: risk if bonuses decrease, and slightly higher total interest on the bonus portion.
What is the best loan period?
Shorter periods mean less total interest but higher monthly payments. Ideally, keep monthly payments under 25% of take-home pay while choosing the shortest period possible.
How much down payment should I make?
Generally 10-20% of the property price. More down payment means less borrowing and less interest, but balance with tax deduction benefits which apply to the loan amount.
What is a safe debt-to-income ratio?
Below 20% is very safe, below 25% is safe. Above 30% puts significant strain on household finances. Check the Reverse tab to verify your ratio.
Term reduction or payment reduction - which is better?
Term reduction generally saves more on interest. Payment reduction is better if you need to lower monthly burden. Compare both in the Prepayment tab.
Is my data safe?
Yes, all calculations run entirely in your browser. No data is sent to any server.
What can I see in the yearly repayment table?
It lists each year's payment, principal portion, interest portion, and loan balance (plus the deduction amount when the mortgage tax deduction is enabled). Switching between Equal Installment and Equal Principal lets you compare early interest burden and how the balance declines. All figures are estimates.
How are total payment and total interest calculated?
They are estimates summing every monthly payment over the full term (including bonus payments when set). Real costs also include handling fees, guarantee fees, and group credit life insurance, so treat the results as a guide. This tool provides general information, not advice on any specific financial product.

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Related Guides

How to Choose a Mortgage: Variable vs. Fixed Rates, Repayment, Deduction A clear guide to choosing a mortgage: variable vs. fixed rates, equal-payment vs. equal-principal methods, safe debt-to-income guidelines, prepayment, and the tax deduction. How Effective Is Mortgage Prepayment? Term-Shortening vs. Payment-Reduction Learn how much interest mortgage prepayment can save, from the basics: the difference between term-shortening and payment-reduction types, how interest is reduced, why earlier is more effective, balancing with cash reserves, the trade-off with loan insurance and tax deductions, and points to check first.