🏥 Japan NHI Premium Calculator
Estimate your annual National Health Insurance (NHI / 国民健康保険) premium in Japan from your household income and the number of insured members. A quick educational estimate before checking your municipality's exact bill.
What is this tool?
National Health Insurance (国民健康保険, Kokumin Kenkō Hoken, or NHI) is the public healthCoverage program for people in Japan who are not enrolled in employer-sponsored insurance — typically the self-employed, retirees, farmers, and their families. Unlike 協会けんぽ or company health insurance, NHI is administered independently by each municipality (市町村), which means premiums differ drastically across Japan's 1,741 local governments. The premium is not a single national rate but a combination of four components: 所得割 (an income-based portion), 資産割 (an asset-based portion on property), 均等割 (a flat per-person portion), and 世帯割 (a per-household portion). Because each town sets its own rates within a national framework, two households with identical incomes can pay very different premiums depending on where they live. This calculator estimates the two most common components — 所得割 and 均等割 — using representative national averages so you can plan ahead. For the exact figure, always consult your municipality's 保険料率表 or the official NHI section on your city's website. If you also want to see how employer insurance differs, compare with our health insurance rate tool, and pair this with the income tax calculator to understand your total burden.
How it works
The calculator builds the premium from two parts. First, the 所得割 (income portion) applies a representative rate of about 7.5% to your taxable income base — defined here as your household income minus a ¥430,000 basic deduction. Second, the 均等割 (flat portion) charges roughly ¥43,000 per insured member per year (capped at six members). An optional 資産割 can be added at about 10% of declared property value where applicable. The total annual premium is the sum of these parts. Municipalities may also apply reductions for low-income households (軽減制度) that this simplified model does not capture.
| Component | Basis | Representative rate |
|---|
NHI premium reduction tiers (軽減制度) for low-income households Eligibility is set by each municipality from the prior-year household income; the 7割 tier typically applies to the lowest-income households. This calculator does not model these reductions, so actual premiums can be far lower.
| Reduction tier | Income portion (所得割) | Per-person portion (均等割) |
|---|---|---|
| 7割 reduction (70%) | −70% | −70% |
| 5割 reduction (50%) | −50% | −50% |
| 2割 reduction (20%) | −20% | −20% |
| --- | --- | --- |
|---|
| 所得割 | max(0, income − ¥430,000) | ~7.5% |
|---|
| 均等割 | per insured member | ~¥43,000 / year |
|---|
| 資産割 | declared property value | ~10% (optional) |
|---|
How to use
- Enter your household's total annual income in 万円 (ten-thousands of yen).
- Enter the number of NHI-insured members in the household (cap 6).
- Optionally enter declared property value in 万円 if your municipality uses 資産割.
- Click Calculate to see the estimated annual premium breakdown.
- Compare the result with your municipality's official 保険料率表 for the exact figure.
Frequently Asked Questions
Why does my NHI premium differ from a friend's with the same income?
NHI is run by each municipality, not the national government. Every city, town, and village sets its own 所得割 and 均等割 rates within a national framework, so premiums for identical incomes vary widely across Japan's 1,741 municipalities.
What is the basic deduction used in the income portion?
This estimate uses a ¥430,000 basic deduction (基礎控除) from your household income before applying the 所得割 rate, matching the common municipal calculation base. Your municipality may use a slightly different figure.
Are there reductions for low-income households?
Yes. Municipalities apply 軽減制度 tiers (commonly 7割 / 5割 / 2割 reductions) to the 所得割 and 均等割 for low-income households. This calculator does not model those tiers, so actual premiums can be far lower for qualifying households.
Does NHI cover everyone in the household together?
Premiums are assessed per household. The 均等割 is charged per insured member (capped), while the 所得割 is based on total household income, so family composition directly affects the bill.
Is this the same as company health insurance?
No. Employees enrolled in 協会けんぽ or company plans pay through payroll (see our health insurance rate tool). NHI is for people outside those plans — the self-employed, retirees, and their families.
This tool is for informational purposes only and does not constitute financial advice. Consult a qualified financial professional for advice specific to your situation.
Tips & Advice
NHI premiums are calculated once a year based on the previous year's income, so a bonus or side income in one year shows up in the next year's bill. If your income dropped sharply (e.g., you left a job), file a 減額申請 (reduction application) with your municipality — many households qualify for the 7割/5割/2割 軽減 tiers that cut the 均等割 and 所得割 substantially. Couples and families are assessed as a single household, so adding a non-working spouse or child as a dependent changes the 均等割 count but not your income base. Finally, NHI is separate from the 介護保険 (long-term care) premium that anyone aged 40–64 also pays — use our long-term care insurance tool to estimate that piece. Always verify the final amount against the statement your city mails you each summer.
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Sources & References
Last reviewed August 2026.
- Ministry of Health, Labour and Welfare — National Health Insurance (Kokumin Kenkō Hoken).
Limitations
Disclaimer: This tool provides a planning estimate using representative national average rates. Actual NHI premiums are set by each municipality and include local reductions, 資産割, and 世帯割 that this model simplifies. It does not constitute insurance, tax, or legal advice. Always confirm the exact amount with your municipality's official statement before making financial decisions.