What you can use here
Five everyday tools on one page. A scientific calculator with trigonometry and logarithms, four kinds of percentage calculation, BMI in metric or imperial units, date arithmetic that handles month-end properly, and a unit converter covering length, weight, temperature, pressure, fuel economy and more.
Enter an amount, a term and a rate to compare four repayment structures — equal payment, equal principal, interest-only and graduated. You get the monthly figure, the total interest, and a period-by-period table showing exactly how the balance comes down. Works in eleven currencies.
A mobile app that maps public toilets across South Korea from official government open data. It centres on your location, sorts the nearest options by distance and hands off to your maps app for walking directions. Particularly handy if you are travelling in Korea.
Why the loan calculator is different
Most calculators give you a monthly payment and stop there. That single number hides the thing that actually costs you money: how the split between interest and principal changes over the life of the loan, and how much that split differs between repayment structures.
So this one shows the whole schedule. Run the same loan through all four tabs and you can see the total interest change — often dramatically. On a long term, the difference between paying down principal evenly and deferring it to the end can amount to a large fraction of what you borrowed in the first place.
Everything runs in your browser. Nothing you type is sent anywhere, stored, or used to generate a quote or a sales call.
About this site
ho1 is a small independent project. It started as a Korean-language site with calculators built around Korean tax and insurance rules, and these English pages cover the parts that work the same way regardless of where you live — loan arithmetic is loan arithmetic — plus the app, which is genuinely useful to anyone visiting Korea.
There is no paywall, no registration, and no premium tier. If something is wrong or you want a tool that does not exist yet, the contact page is the place to say so.
Looking for the Korean-language calculators, including the 2026 net salary calculator? They are on the Korean site.