Kuupy Online Tools
Free online developer tools and calculators. No sign-up required.
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Developer Tools
AES Encrypt/Decrypt
CBC/GCM/CTR/ECB modes with 128/192/256-bit keys, Base64 or Hex output
App Icon Maker
Upload one image to generate all iOS and Android app icon sizes
Base64 Encode/Decode
Encode and decode Base64 online, with full UTF-8 support
Color Converter
Convert colors between HEX, RGB and HSL with live preview, picker and one-click copy
Cron Parser
Parse and build 5-field cron expressions with plain-language breakdowns and upcoming run times
Data Format Converter
Convert between JSON, XML and YAML online
JSON Formatter
Format, minify and validate JSON online with error locating
JWT Encode/Decode
Decode JWT header/payload online, sign and verify HS256/384/512
QR Code Generator & Decoder
Generate QR codes from text or URLs, or decode QR codes from images โ all locally in your browser
SQL to GORM
Paste MySQL CREATE TABLE statements and generate Go GORM model structs
Timestamp Converter
Convert Unix timestamps to dates and back, with a live current timestamp
Calculators
Basic Calculator
Everyday arithmetic: add, subtract, multiply, divide and percent
BMI Calculator
Compute BMI from height and weight, with WHO categories and healthy weight range
BMR & TDEE Calculator
Estimate basal metabolic rate and daily calorie needs with the Mifflin-St Jeor equation
Body Fat Calculator
Estimate body fat percentage from height and circumference measurements using the US Navy method
Countdown Calculator
See how many days remain until any date โ or how many have passed
Dosage Calculator
Calculate per-dose and daily medication amounts by body weight (for reference only; always follow professional advice)
Due Date Calculator
Estimate your due date, pregnancy week and trimesters from your last period
Engineering Calculator
Engineering notation and unit conversion for length, weight, temperature and more
Mortgage Calculator
Calculate monthly payment, total interest and amortization schedule
Ovulation Calculator
Predict ovulation dates and fertile windows from your last period and cycle length
Programmer Calculator
Binary/octal/decimal/hex conversion and bitwise operations
Scientific Calculator
Trigonometry, logarithms, powers and expression evaluation
Sleep Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles
Workday Calculator
Add N business days to a date, or count business days between two dates
Zodiac Sign Calculator
Enter your birth date to find your zodiac sign, date range and traits