Free calculators, converters and developer tools that run right in your browser. No sign-up, no install — what you type never leaves your device.
Count characters with and without spaces, words and bytes, and check X, meta description and SMS limits.
↗Annual salary in won to monthly net pay after Korean social insurance and income tax (2026).
↗Gross monthly pay in Korea to net salary after pension, health, employment insurance and tax.
↗Statutory severance pay (toejikgeum) in Korea from your dates of service and last 3 months' wages.
↗Weekly holiday pay (juhyu sudang) for part-time jobs in Korea from hourly wage and weekly hours.
↗Monthly payment and total interest for amortized, equal-principal and interest-only loans.
↗X% of a number, what percent A is of B, percent change, increase/decrease and original price.
↗Can't decide what to eat? Spin the food roulette wheel. Pick a set (quick lunch, Mexican, Italian, Asian, Korean, healthy) or add your own options.
↗Annual salary in won to monthly net pay after Korean social insurance and income tax (2026).
↗Gross monthly pay in Korea to net salary after pension, health, employment insurance and tax.
↗Statutory severance pay (toejikgeum) in Korea from your dates of service and last 3 months' wages.
↗Paid leave days earned under Korean labor law, plus the cash value of your unused annual leave.
↗Weekly holiday pay (juhyu sudang) for part-time jobs in Korea from hourly wage and weekly hours.
↗Korean job-seeking allowance for 2026: daily amount, benefit days and total, with cap and floor.
↗Monthly payment and total interest for amortized, equal-principal and interest-only loans.
↗Month-by-month table of principal, interest and balance for any loan, with CSV copy.
↗Interest and after-tax maturity value when you deposit the same amount every month.
↗Interest, tax and maturity value for a CD, fixed deposit or time deposit.
↗X% of a number, what percent A is of B, percent change, increase/decrease and original price.
↗Add or remove Korea's 10% VAT (÷ 11), plus a simplified taxpayer VAT estimate. In KRW.
↗Net pay after Korea's 3.3% freelance withholding tax, reverse gross-up and 8.8% comparison.
↗Hourly wage to weekly, monthly and annual pay in Korea with holiday pay, vs the 2026 minimum wage.
↗Future value with monthly contributions, year-by-year table, APY and the rule of 72.
↗2026 Korean National Pension, health, care and employment insurance for employee and employer.
↗Acquisition tax, education tax and rural tax when buying a home in South Korea (2026 rates).
↗Legal maximum agent commission in Korea for a sale, jeonse or monthly rent, with optional VAT.
↗Annual Korean housing property tax from the official price, split into July and September bills.
↗Monthly mortgage payment, total interest and LTV, plus the income a Korean bank needs for 40% DSR.
↗Loan-to-value ratio and maximum mortgage by region and home count under Korea's 2026 LTV rules.
↗Debt-to-income ratio with new and existing mortgages, and the largest mortgage within a DTI limit.
↗Debt service ratio across all your loans and the largest new loan within the 40% limit, with stress DSR.
↗Convert a Korean jeonse deposit to monthly rent (wolse) and back, and check the legal conversion cap.
↗Exact age in years, months and days, days until your next birthday, plus Korean age explained.
↗Countdown to any date or days since a past date, with 100-day, 1,000-day and yearly milestones.
↗Days between two dates in days, weeks, months and years, plus weekdays (Mon–Fri) and weekend days.
↗Add or subtract days, weeks, months, years or business days from a date and get the weekday.
↗Weekly hours, overtime and 10 PM–6 AM night work from shift times, with pay under Korean labor law.
↗Discharge date, days left and percent served for South Korean Army, Navy, Air Force and Marines.
↗Best bedtime or wake-up time based on 90-minute sleep cycles, plus power nap alarm times.
↗Day count since you got together and your 100-day, 1,000-day and yearly anniversaries, Korean style.
↗Due date and weeks pregnant from your last period, conception date or known due date, with trimesters.
↗Estimated ovulation day, fertile window and next period for the next 3–4 cycles from your cycle length.
↗Baby's age in days, weeks and months, with 100th-day and birthday dates and corrected age for preemies.
↗How much formula per day and per bottle (oz and mL) by baby's weight and age, with a feeding chart.
↗Monthly South Korean parental leave benefit for 2026, including the 6+6 plan and single-parent caps.
↗Free BMI calculator in lb and ft/in or kg and cm. See your WHO/CDC weight category, healthy weight range for your height, Asian cutoffs and waist-size risk.
↗Solve proportions (A:B = C:?), simplify ratios by the GCD, split money by a ratio like 60:40, and find screen aspect ratios such as 16:9 — free ratio calculator.
↗Free GPA calculator: enter credits and letter grades to get your unweighted and weighted GPA on a 4.0 scale, plus 4.3/4.5 scale and percent conversions.
↗Calculate gas cost for a trip or monthly commute from miles, MPG and price per gallon, and find your real MPG from a fill-up. Metric km/L and L/100 km too.
↗Free online scientific calculator with sin, cos, tan and inverses (DEG/RAD), ln, log, log2, roots, powers, factorials, memory, history and keyboard input.
↗Free unit converter: convert length, weight, area, volume, temperature, speed and data size into every unit at once — inches, lbs, °F, gallons, mph, GB and more.
↗Convert length between cm, mm, meters, km, inches, feet, yards, miles and nautical miles instantly, with a common length conversion chart and height in feet and inches.
↗Convert weight between kilograms, pounds, ounces, grams, stone, tons and carats instantly, with a common weight conversion chart, formulas and quick mental-math tips.
↗Convert between Celsius, Fahrenheit and Kelvin instantly. Includes the formulas, a common temperature chart for weather, body and oven temperatures, and mental-math tricks.
↗Convert area between square feet, square meters, acres, hectares, square miles, square yards and the Korean pyeong instantly, with a common area conversion chart.
↗Convert speed between miles per hour, kilometers per hour, meters per second, knots, feet per second and Mach instantly, with a chart of common speed limits and speeds.
↗Convert pyeong (평), the Korean apartment size unit, to square meters and square feet. 1 pyeong = 3.3058 m². Includes 25- and 34-pyeong apartment sizes explained.
↗Convert square meters (m²) to pyeong, the size unit used for Korean apartments. See how many pyeong 59 m² and 84 m² are and the usual size label for each listing.
↗Convert kilograms to pounds instantly: 1 kg = 2.20462 lbs. Includes a kg to lbs chart for body weight, pounds and ounces, luggage limits, gym plates and a mental-math trick.
↗Convert pounds to kilograms instantly: 1 lb = 0.4536 kg. Includes a lbs to kg chart, gym plate weights, recipe amounts, baby weights in lb and oz, and a quick mental-math trick.
↗Convert centimeters to inches instantly: 1 cm = 0.3937 inches. Includes a cm to inches chart, height in feet and inches, waist sizes and fractional inches to 1/8.
↗Convert inches to centimeters instantly: 1 inch = 2.54 cm. Includes an inches to cm chart, fractions of an inch, and the real width and height of TV and monitor sizes.
↗Convert Celsius to Fahrenheit instantly with the formula °F = °C × 9/5 + 32. Includes a °C to °F chart for weather, body temperature and oven settings, plus a mental-math trick.
↗Convert Fahrenheit to Celsius instantly with °C = (°F − 32) × 5/9. Includes a °F to °C chart for weather, oven temperatures like 350 °F, body temperature and fridge settings.
↗Count characters with and without spaces, words and bytes, and check X, meta description and SMS limits.
↗Count words, sentences and paragraphs, estimate reading and speaking time, and find your most-used words.
↗Collapse double spaces, strip all whitespace or trim lines — tabs, non-breaking and zero-width spaces too.
↗Fix text copied from PDFs: join broken lines with spaces or commas while keeping paragraphs and list items.
↗Convert text to UPPERCASE, lowercase, Title Case, camelCase, snake_case, kebab-case and more in one go.
↗Dedupe any list, ignoring case and spaces, then sort A–Z or by frequency — or show only the duplicates.
↗Compare two texts side by side and highlight added, removed and changed lines down to the word or character.
↗Type Korean on an English keyboard: turn QWERTY keys like dkssud into Hangul, or Hangul back into keys.
↗Free online JSON formatter: pretty print JSON with 2-space, 4-space or tab indentation, or minify it to a single line. Runs entirely in your browser.
↗Decode Base64 to text or encode text to Base64 instantly. Handles UTF-8 (accents, emoji) and URL-safe Base64URL, with or without padding. Runs in-browser.
↗Test regular expressions as you type: live match highlighting, capture and named groups, replace preview and a clickable cheat sheet. JavaScript flavor.
↗Convert HEX to RGB and HSL and back, generate a 50–950 shade palette, and check WCAG AA/AAA contrast ratios. A free color converter for designers and devs.
↗Paste a JSON Web Token to decode its header and payload and read exp, iat and nbf as local and UTC times. Your token never leaves the browser.
↗Convert Unix epoch timestamps to readable dates in your local time and UTC, or a date to epoch. Auto-detects seconds, milliseconds, μs and ns.
↗Validate JSON as you type and pinpoint syntax errors by line and column, with plain-English hints for trailing commas, quotes and comments, plus auto-fix.
↗URL encode or decode text and links online. Choose encodeURIComponent or encodeURI, handle + for spaces, and see query parameters decoded in a table.
↗Generate random UUID v4 or time-ordered UUID v7 in bulk, up to 1,000 at once. Uppercase, no-hyphen, GUID braces, JSON or SQL output, plus a UUID inspector.
↗Generate strong random passwords (8–64 chars) or memorable passphrases. Pick character sets, skip look-alikes like 0/O, and see entropy and crack time.
↗Convert binary, octal, decimal, hex and any base 2–36 instantly. BigInt precision, two's complement for 8–64-bit, clickable bits and 0x/0b prefixes.
↗Free calorie calculator: enter age, height (ft/in or cm) and weight (lb or kg) to get BMR, TDEE maintenance calories, weight-loss targets and macros.
↗Tip calculator: enter the bill, pick 15, 18, 20 or 22% and split it between friends. Round up per person, compare tip amounts and see US tipping etiquette.
↗Percent off calculator: find the sale price, % off between two prices, stacked discounts (20% + 10%), the original price before a sale and BOGO deals.
↗Enter a birth year to get the Chinese/Korean zodiac animal, element and stem-branch name, age this year and school grade, plus a year-by-year chart.
↗Estimate your Korean electricity bill from monthly kWh: KEPCO 3-tier progressive residential rates, summer tiers, climate and fuel charges, VAT, in KRW.
↗Can't decide what to eat? Spin the food roulette wheel. Pick a set (quick lunch, Mexican, Italian, Asian, Korean, healthy) or add your own options.
↗Random lottery number generator for Korea Lotto 6/45, Powerball, Mega Millions or a custom range. Fix or exclude numbers, make 10 lines, see the odds.
↗Play the ladder game (Amidakuji, Ghost Leg) online with 2–12 players. Enter names and prizes, watch each path animate, and get provably fair results.
↗Paste a list of names to pick random winners, split people into random teams (by count or size) or shuffle a turn order. Fair, no repeats, easy to copy.
↗Play the 2048 puzzle game free in your browser. Merge tiles with arrow keys, WASD, or swipe to reach 2048. Best score saved, plus corner strategy tips.
↗Click the moment the screen turns green. This reaction time test measures your reflexes in ms over 5 tries and shows your average, best, and rating.
↗Play classic Minesweeper online free, no download: Beginner 9×9, Intermediate 16×16, Expert 30×16. Flag with right-click or long-press. Best times saved.
↗Free typing speed test: type 5 short English sentences and get your words per minute (WPM) and accuracy. See how WPM is calculated and how to type faster.
↗Memorize a number shown for a few seconds, then type it back. Starts at 3 digits and adds one each round. A free short-term memory test with memory tips.
↗Play the classic Snake game online free. Eat to grow longer and faster, grab golden bonus food, and avoid the walls. Arrow keys, WASD, swipe, or buttons.
↗Free 3D airplane dogfight game in your browser. Up to 6 players connect peer-to-peer. Invite friends with a room code, quick match, or practice vs AI bots.
↗Free brain training games in large print: card match, color words, sequence memory, simple math, and a grocery list. Track your 7-day scores and streak.
↗smith lab is a free collection of tools for the calculations and conversions people need every day — from salary and loan math to dates, units, text and developer utilities. Every calculation runs in your browser, and the values you enter are never sent to a server.
smith lab started in South Korea, so some money, real-estate and parenting tools follow South Korean rules (KRW, Korean tax and insurance rates). Each of those pages says which rules it uses. The Korean site also has 115 tools and a blog with 329 articles (in Korean).
Results are estimates for reference. For important decisions about taxes, loans or pay, double-check with official sources or a professional.