Online Tools for Developers

Fast, free tools right in your browser. No sign-up, no data sent to servers — everything runs locally.

Cryptography & Hashing

MD5 Hash Generator

Generate MD5, SHA-1, SHA-256, SHA-512 hashes and more from any text.
Date & Time

Unix Timestamp Converter

Live current Unix time, convert dates to Unix timestamps and Unix timestamps to readable dates.
CSS Tools

CSS Gradient Generator

Create linear and radial CSS gradients visually with live preview and copy the generated code.

CSS Border-Radius Generator

Visually adjust rounded corners — individual corners, elliptical radii, with live preview.
PHP

PHP date() & strtotime()

Interactive reference: test format strings live, look up parameters and try strtotime() expressions.

Why CalcSI?

100% Local

All calculations run directly in your browser. No data ever leaves your computer.

Ready Instantly

No registration, no login, no ads. Just open and start using.

Responsive

Works on desktop, tablet and smartphone — anywhere, anytime.