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: 2026/03/02 Finance
JPY
%
Rate Presets
yrs
JPY
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.

Tax deduction amounts are estimates for 2024 move-in. Consult a tax professional for details.

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

JPY
years later
Prepayment Effect
Repayment Chart

Results are estimates and may differ from actual loan terms.

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

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 tax deduction settings.

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 SupportAuto-calculate deductions based on 2024 rules by housing type.
  • 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

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?
For 2024 move-in, 0.7% of the year-end loan balance is deducted from income/resident taxes for 13 years. Limits vary by housing type (Certified: 50M, ZEH: 45M, Energy-saving: 40M, Other: 30M JPY).
Should I prepay during the tax deduction period?
Since deductions are based on year-end balance, prepaying during the deduction period reduces your deduction. 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.

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