About smith lab

smith lab is a free collection of web tools built so you can finish everyday calculations, conversions and checks in one place. It was started in October 2026 by a single developer with one rule — "if I do it three times, I build a tool for it." The English site has 92 tools, and the Korean site has 115 tools plus 329 articles.

What we offer

• Money — salary and take-home pay, severance, unused leave and weekly holiday pay, loan interest and amortization, savings and deposit interest
• Real estate — acquisition tax, brokerage fees, property tax, mortgages, LTV·DTI·DSR
• Dates and parenting — age, D-Day, date differences, work hours, pregnancy weeks, ovulation, baby age
• Calculators and everyday tools — BMI, ratios, percentages, calories, discounts, tips and bill splitting
• Converters, text and developer tools — unit conversion, character counts, JSON, Base64, URL encoding, UUID, regex
• Games and social media — browser mini games and small social media helpers

Many money, real-estate and parenting tools follow South Korean rules (KRW, Korean tax and social insurance rates). Each page says which rules and which year it uses.

Principles

• No install, no sign-up — open a page and use it right away.
• Your input stays in your browser — values you type into a calculator are processed only in your browser and are not sent to our server. The one exception is the optional AI photo analysis on the Korean site, which you turn on yourself; it is described separately in our Privacy Policy.
• Open about the math — results come with the formula, the reference year and the rates used.

How we make our content

• Sources — tax rates, insurance rates, rules and health standards are based on official sources (for example Korea's National Tax Service, National Pension Service, National Health Insurance Service and Korea Disease Control and Prevention Agency) and research, and pages state the source and reference year.
• Calculated, not guessed — example amounts and tables are calculated with the same formulas the tools use. Examples that are not real statistics are labeled as examples.
• Kept up to date — rules that change every year (minimum wage, insurance rates and so on) are updated in both the tools and the articles, with the date of the change.
• Information, not advice — health content does not replace a diagnosis, and money content does not recommend specific products.

How the site is run

smith lab is a static website; its source code lives on GitHub and it is served through Cloudflare. Running costs may be covered by advertising (Google AdSense). Ads are clearly separated from content, and values you enter into calculators are never sent to advertising or analytics services.

Please note

Tax rates, insurance rates, lending rules and the minimum wage change every year. Every tool shows its reference date, but results are for reference only and actual amounts can differ depending on how agencies, employers and banks calculate them. Before an important decision, please check with official sources and professionals.

If you find a wrong result or an outdated rule, please let us know via the Contact page. We'll fix it as soon as we confirm it and note the date of the fix.