Percentage Calculator
Three common percentage calculations in one place.
Tip Calculator
Bill total, tip %, and number of people — get per-person amounts instantly.
Discount Calculator
Original price + discount % → final price and savings.
Age Calculator
Exact age in years, months and days — plus days until your next birthday.
BMI Calculator
Body Mass Index with WHO categories: <18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, ≥30 obese.
Compound Interest Calculator
Initial deposit + monthly contributions, compounded monthly.
Loan / Mortgage Calculator
Monthly payment, total interest and payoff for a fixed-rate loan.
Unit Converter
Length, weight and temperature conversions.
Date Difference Calculator
Days between two dates, or add/subtract days from a date.
① Difference
② Add / subtract days
Password Generator
Strong random passwords generated locally in your browser — nothing is sent to any server.
Word Counter
Words, characters, sentences and reading time — great for essays, posts and tweets.
QR Code Generator
Turn any URL or text into a QR code, generated locally in your browser.
JSON Formatter
Beautify or minify JSON.
Calorie Calculator
Mifflin-St Jeor equation for BMR and daily calorie needs (TDEE), plus cutting/bulking targets.
Pregnancy Due Date Calculator
Naegele's rule: estimated due date = first day of last menstrual period + 280 days.
Random Number Generator
Cryptographically random integers in any range — great for giveaways and raffles.
Base64 Encoder / Decoder
Convert text to and from Base64 (UTF-8 safe).
Color Picker
Pick a color and get HEX, RGB and HSL values — handy for design and front-end work.
Image Compressor
Compress JPG/PNG/WebP entirely in your browser — images never leave your device.
Merge PDF
Combine multiple PDF files into one, in order — processed entirely in your browser.
Split PDF / Extract Pages
Extract a page range from a PDF into a new file.
Coordinate Converter (WGS-84 / GCJ-02 / BD-09)
Convert between GPS coordinates (WGS-84), the GCJ-02 datum used by Chinese map providers (AMap/Tencent, a.k.a. "Mars coordinates"), and Baidu's BD-09 datum.
Standard public algorithms; GCJ-02 → WGS-84 uses iterative inverse with ~1 m accuracy. Coordinates outside mainland China are returned unchanged.
Latitude/Longitude Converter (Decimal ↔ DMS)
Convert decimal degrees (DD) to degrees-minutes-seconds (DMS) and back, e.g. 116.397428° = 116°23′50.7″ E.
① Decimal → DMS
② DMS → Decimal
GeoJSON Coordinate Batch Converter
Upload or paste a GeoJSON file and batch-convert every coordinate (Point / LineString / Polygon / FeatureCollection) between WGS-84 / GCJ-02 / BD-09 — processed entirely in your browser.
UTM Projection Converter (WGS-84 ↔ UTM)
Convert latitude/longitude (WGS-84) to and from UTM grid coordinates (Easting / Northing) using standard Transverse Mercator formulas (k₀ = 0.9996). Zone is auto-detected from longitude, or set it manually.