Convert tools

Calculate your Body Mass Index from height and weight, with the classification under either the Japan Society for the Study of Obesity (JASSO) standard or the WHO standard. The result includes the ideal weight (BMI 22), the healthy weight range (BMI 18.5–25), and the difference from the ideal. Toggle the standard with a Mode, and the unit system between metric (cm / kg) and imperial (inch / lb) with an Option. Live computation as you type — everything stays inside your browser.

Cross-reference clothing sizes across Letter (XS / S / M / L / XL / XXL / 3XL), Japan (号 or cm), US, UK and EU. Switch between four charts (Men × Women × Tops × Bottoms) — tops use chest, bottoms use waist, both shown with the body measurement in cm. Useful when shopping at Amazon US / ASOS / H&M / Marks & Spencer from Japan or vice versa. Type a value to highlight the matching row. Tables are a composite of UNIQLO / MUJI / Marks & Spencer / H&M, with the usual 0.5–1 size brand variation (see FAQ). Runs entirely in your browser — no uploads.

Convert vehicle fuel economy between km/L (Japan, Nordic), L/100km (Europe, China, Australia), mpg US, and mpg UK. Handy when comparing a Japanese spec sheet against an EU/US one, or translating a rental car's mpg dashboard into km/L. Uses exact NIST factors (1 mile = 1.609344 km, 1 US gal = 3.785411784 L, 1 UK gal = 4.54609 L). Runs entirely in your browser — no uploads.

Convert a color temperature (Kelvin, 1000K–40000K) into RGB / HEX / mired and inspect how a light source would render — ideal for white-balance, white-point, or interior-lighting workflows. Powered by Tanner Helland's sRGB approximation, with one-click presets for candlelight (1500K), tungsten (2700K), warm fluorescent (3000K), daylight 5000K, standard D65 (6500K), overcast (8000K), and blue sky (10000K). Mired (1,000,000 / K) and a coarse reverse lookup from RGB are also provided. Nothing leaves your browser.

Convert between binary, octal, decimal, and hexadecimal in one step. Toggle the input base (Mode) and the other three are computed instantly. Optional 0b / 0o / 0x prefixes and 4-digit grouping. Powered by BigInt for full precision, all inside your browser.

Look up paper sizes (A4 / B5 / Letter / Legal / postcard / business card / envelopes) with millimetres, centimetres, inches, points, and pixel dimensions at 72 / 96 / 150 / 300 / 600 DPI. Distinguishes ISO 216 (A / B / C series) from JIS B; includes Japanese photo formats (L / 2L / KG) and postal envelope standards. Search across names, aliases, and notes with a series filter. Useful for print, DTP, PDF export, and image sizing decisions.

A general-purpose percentage tool with four modes: X% of Y, X as % of Y, percent change from A to B, and a value increased or decreased by N%. Use it for discounts, year-over-year change, success rates, custom tax rates, tips, or grade percentages — all in one screen. Live calculation, 0 to 10 decimal places, and one-click copy. Everything runs in your browser.

Convert recipe quantities between Japanese (tsp 5 ml, tbsp 15 ml, cup 200 ml, gō 180 ml) and US (tsp 4.93 ml, tbsp 14.79 ml, cup 236.59 ml, fl oz 29.57 ml) units side-by-side. Weight units (g, kg, oz, lb) sit in a separate Mode. Handy when cooking a US recipe with Japanese measuring tools — the JP cup is **~18% smaller** than the US cup, a gap big enough to spoil sauces and bakes. Volume and weight stay separate because the conversion depends on ingredient density (see FAQ). Runs entirely in your browser — no uploads.

Convert ring sizes between Japan 号 (1–29), inner diameter (mm), US, UK (Wheatsheaf A–Z+), and EU (inner circumference mm). Handy when sizing a Tiffany / Cartier / BVLGARI / Pandora ring sourced from abroad, or when measuring an existing ring with a caliper. UK accepts letters (K / K1/2 / K½) or the numeric position (11.5). Internally everything is normalised to inner circumference and linearly interpolated from the published odd-number Japanese chart. Brands vary by 0.25–0.5 sizes — always double-check the maker's own diameter (mm) chart for a critical purchase such as an engagement ring. Runs entirely in your browser — no uploads.

Convert between Arabic numbers (1–3999) and Roman numerals (I / V / X / L / C / D / M). Covers the standard range used for year labels, chapter numbers, watch dials, and sequel titles. Runs entirely in your browser — no uploads.

Convert shoe sizes between Japan (cm, Mondopoint), US, UK and EU. Handy when buying Nike, Adidas, New Balance, Vans, Dr. Martens or Birkenstock from overseas shops, or sanity-checking a gift bought abroad. Choose Men / Women / Kids with the radio buttons — the conversion table follows the Brannock device and major brand charts, but individual brands vary by ~0.5 sizes, so always double-check with the maker's own chart for a critical fit. Runs entirely in your browser — no uploads.

Convert between length, weight, temperature, volume, area, speed, data size, and time units. Enter one value and see equivalents in every supported unit at once. Runs entirely in your browser — no uploads.