About
so-yi tools is a collection of calculators and converters that run entirely in your browser. No install, no sign-up.
The site is primarily built for Korean users — most calculators encode Korean tax rules, insurance rates, and utility tariffs. The developer tools are language-independent and available in English.
Three principles
1. Your input never leaves your browser
Everything you type or upload — salaries, loan amounts, image files, JSON, tokens — is processed locally in your browser. Nothing is sent to a server, and nothing is stored.
That includes file-based tools. Image compression uses the Canvas API and hashing uses the Web Crypto API, both running on your device, so these tools work with your network disconnected.
The one exception is the currency converter, which fetches current exchange rates from an external source. Even there, the amount you enter is never transmitted.
2. Every calculation shows its basis
Where a calculation rests on published rules — tax brackets, insurance rates, utility tariffs — the page explains exactly how the number was derived, cites the source, and states the reference year. Where a figure is an approximation, the page says so and explains why it may differ from the official result.
The goal is that you can check the arithmetic yourself, not just take a number on faith.
3. Reference values are refreshed every year
Insurance rates, the minimum wage, income tax brackets, and electricity tariffs all change annually in Korea. These constants live in a separate file from the code and are reconciled against official notices each January and July.
Every tool displays its reference year and last-updated date at the bottom.
On accuracy
Financial and tax results are for reference only and carry no legal weight.
Actual amounts vary with individual deductions, employer policy, and regional rates. For anything binding, confirm with the relevant authority.
Found an error?
If a calculation is wrong or a rate is out of date, please tell us. Accuracy is the whole point of this site. See the contact page.
How the site is funded
Advertising covers hosting and maintenance. Ads are kept out of the way:
- No ads inserted between form fields
- Ad slots reserve their space so the page never jumps
- No interstitials and no autoplay video