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If you’ve ever stared at a Korean payslip wondering why your net pay is smaller than your contract number, you’re looking at the four social insurances. A 4대보험 calculator does one job: it takes your monthly gross pay and estimates the four mandatory deductions before income tax even enters the picture. Useful, yes. But the output is only as good as the number you feed it, and most people feed it the wrong one.

This is a walkthrough of what a calculator is really doing behind the button, so you can read your own slip instead of trusting a website blindly.

Key takeaways

The four insurances are National Pension (국민연금), Health Insurance (건강보험), Employment Insurance (고용보험), and Industrial Accident Insurance (산재보험).
Three of them are split between you and your employer; 산재보험 is paid entirely by the employer, so it never comes out of your pay.
Calculators run on your monthly gross salary, but each insurance uses a slightly different base, which is why the math never lines up to a single clean percentage.
Rates change each year. A 2026 result from an old calculator can be off, so confirm the current rates before trusting a figure.
This applies to foreign workers too, with a few National Pension exceptions tied to your nationality.

What the four insurances actually are

People say “4대보험” like it’s one thing. It’s four separate systems with different purposes and different math.

National Pension (국민연금) — retirement income. You and your employer each pay half of the pension contribution.
Health Insurance (건강보험) — medical coverage. Split with your employer. There’s also a Long-Term Care add-on calculated as a percentage of your health premium, not of your salary.
Employment Insurance (고용보험) — this is what funds unemployment benefits (실업급여). The unemployment portion is split; employers pay an extra slice for job-security and training programs that you don’t.
Industrial Accident Insurance (산재보험) — covers work injuries. The employer pays 100%. If you see it deducted from your pay, something is wrong.

That last point matters more than people realize. When a calculator shows your personal deduction, it should include only pension, health, long-term care, and your share of employment insurance. Nothing for 산재보험.

Which number do you type in?

Here’s where most calculator results go sideways. The calculator wants your monthly taxable gross, and that is not always your headline salary.

Some allowances are non-taxable and get excluded from the base. The classic example is a meal allowance up to a certain monthly cap, which is treated as non-taxable and therefore isn’t counted for these deductions. If you plug in your full contract amount including a non-taxable meal allowance, the calculator will overstate what comes out of your pay.

So before you type anything, separate your pay into two buckets: taxable wages and non-taxable allowances. Feed only the taxable portion. If you’re not sure which allowances qualify, that’s a question for your HR or payroll team, not a guess.

Why the total never equals one tidy percentage

You might expect “add up the four rates, multiply once, done.” It doesn’t work that way, and understanding why saves you from thinking the calculator is broken.

National Pension applies within a floor and a ceiling. If your income sits above the monthly ceiling, your pension contribution stops growing even as your salary does. High earners notice their pension deduction flatlines.
Health Insurance is a straight percentage of your monthly base, then Long-Term Care is layered on as a percentage of that health premium. Two-step math, not one.
Employment Insurance uses its own rate on your wages.
Rates are set annually and don’t move together. Health might tick up one year while pension holds steady.

Because each insurance has its own base, cap, and rate, the effective total deduction rate on your gross pay lands somewhere in the high single digits for most workers, but the exact figure shifts by salary level. A good calculator does these steps separately and shows a line-by-line breakdown. If it only spits out one lump sum with no breakdown, be suspicious.

A worked example (illustrative, not official rates)

To show the shape of the calculation, here’s a fully hypothetical case. The rates below are placeholders so you can see the structure; do not treat them as the real 2026 numbers.

Insurance line	Base used	Who pays your share?	Shows on your slip?
National Pension	Monthly income within floor/ceiling	You + employer, split evenly	Yes
Health Insurance	Monthly taxable base	You + employer, split evenly	Yes
Long-Term Care	% of your health premium	You + employer, split evenly	Yes
Employment (unemployment)	Monthly wages	You + employer, split evenly	Yes
Industrial Accident	Payroll	Employer only	No

The takeaway from the table isn’t a number. It’s the pattern: four of the five personal-facing lines are shared costs, and each pulls from a slightly different base.

How to sanity-check a calculator result

Treat the calculator as a first estimate, then verify against reality.

Compare the estimate to your actual payslip’s deduction section. If they’re within a small margin, you used the right base.
Confirm 산재보험 is not deducted from your pay. If it is, flag it.
Check that the calculator states which year’s rates it uses. An undated tool is a red flag in 2026.
For an authoritative cross-check, the National Health Insurance Service (건강보험공단) and the National Pension Service (국민연금공단) publish official calculators. When the numbers matter, verify there.

Notes for foreign workers

The default is that foreign employees are covered the same as Korean nationals across all four insurances. Health and employment insurance generally apply to foreign workers on the same terms.

National Pension is the one with variation. Depending on your nationality, coverage can be mandatory, exempt, or subject to a reciprocity arrangement, and some countries have agreements that let you reclaim or credit contributions. A generic calculator won’t know your nationality’s rule, so don’t assume its pension line applies to you. Confirm your specific status with the National Pension Service.

Common mistakes people make

Entering total contract pay instead of taxable pay. Result: the estimate is too high.
Assuming the employer half comes out of your pocket. It doesn’t; only your share is deducted.
Using a calculator built for an old year and trusting the total after rates changed.
Forgetting that pension has a ceiling, then panicking when a raise doesn’t increase the pension line much.
Expecting the calculator’s total to match your take-home. It won’t, because income tax and local tax are separate deductions on top of these four.

FAQ

Does a 4대보험 calculator include income tax?

No. It only estimates the four social insurances. Income tax (소득세) and local income tax are calculated separately and also come off your pay, so your final net will be lower than the calculator’s after-insurance figure.

Why is my employer’s contribution shown at all?

Good calculators show both halves so you understand the full cost of the insurances, but only your share is deducted from your salary. The employer pays their half directly.

I’m a part-timer. Do all four still apply?

It depends on your hours and contract length. Very short or very low-hour arrangements can fall below the enrollment threshold for some insurances. A general calculator assumes standard full enrollment, so check your actual eligibility rather than relying on the estimate.

The calculator result doesn’t match my payslip. What’s wrong?

Most often it’s the input base. You probably entered gross pay including non-taxable allowances. Redo it with only your taxable wages, and confirm the tool uses 2026 rates.

Can foreign workers use the same calculator?

For health and employment insurance, yes. The pension line may not apply the same way depending on your nationality, so verify that portion separately with the National Pension Service.

Use the calculator to get oriented, not to make final decisions. The number that actually governs your paycheck is on your official payslip and in the two public agencies’ own tools. When they disagree with a random website, trust the official source.

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[태그:] Health Insurance Korea

How a 4대보험 (Korea’s 4 Social Insurances) Calculator Actually Works in 2026