Why Does Take-Home Pay Differ Between Calculators?
Most people have had the experience of entering the same pre-tax salary into two calculators and getting two different take-home numbers. The short answer: it's not that one calculator is "wrong" — they're just running different assumptions. Take-home pay isn't computed from secret data; it comes from a public formula (Korea's four major social-insurance rates plus the National Tax Service's simplified withholding table), and different input assumptions into that formula produce different results.
A real example: comparing two calculators
Here's how two widely used take-home tables actually compare for the same salary.
| Pre-tax annual (KRW) | Calculator A (monthly) | Calculator B (monthly) | Difference |
|---|---|---|---|
| 30M | ~2.22M | ~2.25M | B is +30k |
| 50M | ~3.49M | ~3.55M | B is +60k |
| 100M | ~6.42M | ~6.42M | Nearly identical |
The gap is bigger at lower salaries and nearly disappears at KRW 100M. That pattern itself is a clue that "assumptions" are the real cause.
Three assumptions that drive the difference
① Tax-free meal allowance
Up to a certain amount of monthly meal allowance is tax-free (currently KRW 200,000/month). Some calculators assume the full 200,000, others assume the old 100,000 threshold, or zero. A larger tax-free amount shrinks the taxable base, which lowers both social insurance and income tax — and raises take-home pay.
② National pension rate and cap
The employee's national pension contribution rate and the income cap it applies to (the "standard monthly income" ceiling) are adjusted every year. Even a table labeled "2026 rates" sometimes actually uses an older rate, which shows up as a few thousand won of difference at lower salary levels.
③ Number of dependents
The simplified withholding tax table sets a different withholding amount depending on number of dependents. Whether the calculator assumes a single-person household or includes a spouse and children changes the income tax significantly.
So how should you actually read take-home numbers
- Don't fixate on a single "absolute" take-home figure — check which assumptions produced it.
- When comparing a job change, it's most accurate to compute your current and offered salary with the same assumptions side by side and look at the difference.
- Using a calculator that lets you enter your own dependents and tax-free items reduces the error.
※ This article is for general information only, not individual tax advice. Rates and thresholds change over time.