UtilityBox

Free online calculators and everyday utility tools, built with Astro and TypeScript. Static output, no backend required.

Tools

Calculators

• Scientific calculator (trig, logs, powers, roots, constants)
• Currency converter (live rates via the Frankfurter/ECB API)
• Unit converter (length, weight, temperature, volume, area, speed, data, time)
• UK salary calculator (income tax, National Insurance, student loan, pension — 2026/27 bands)
• Percentage calculator (X% of Y, what % is X of Y, percentage change)
• VAT calculator (add/remove UK VAT at any rate)
• Tip calculator (tip amount, total, per-person split)
• Loan/mortgage repayment calculator (monthly payment, total interest)
• Budget calculator (monthly income vs spending, compared with the 50/30/20 guideline)

Networking

• CIDR / subnet calculator (network & broadcast address, host ranges, subnet splitting)
• IPv6 subnet calculator (expand/compress, address classification, subnet ranges)
• IP address converter (dotted decimal ⇄ binary ⇄ hex ⇄ 32-bit integer, auto-detected)
• DNS lookup (live A/AAAA/CNAME/MX/TXT/NS/SOA/SRV/CAA queries via DNS-over-HTTPS)
• DNS record type reference (searchable, A through TLSA)
• HTTP status code reference (searchable, 1xx–5xx)
• Port number reference (searchable common TCP/UDP ports)
• MAC address formatter/validator (colon/hyphen/dot notation, locally-administered/multicast detection)
• Bandwidth / transfer time calculator
• Is It Down? status checker (browser-side reachability test for any site, plus a live board of ~30 popular services read from their public Statuspage feeds, fetched only on click — never on page load, for privacy)

Word Games

• Word unscrambler
• Word builder (with pattern matching and word-game scoring)
• Word/character counter (with reading and speaking time estimates)
• Case converter (UPPER/lower/Title/Sentence/camelCase/PascalCase/snake_case/kebab-case/CONSTANT_CASE/path/case/MoCkInG CaSe)
• Palindrome checker
• Anagram solver

Generators

• Random string generator (passwords, tokens, UUID v4 — uses crypto.getRandomValues)
• UUID generator (v1, v4, v7, nil, max — one or many at once, plus a UUID validator)
• Lorem Ipsum generator
• Color converter (HEX/RGB/HSL + palette generator)
• Slug generator (URL-safe kebab-case/snake_case)
• Placeholder image generator (SVG, no image library needed)
• Dice roller (D3, D4, D6, D8, D10, D12, D20, D100, and D% percentile pair; multiple dice, modifier, D20 advantage/disadvantage; Web Crypto RNG with rejection sampling)
• Playing card randomiser (standard 52-card deck, Fisher-Yates shuffle, draw with or without replacement)
• QR code generator (SVG, hand-written encoder — versions 1-10, byte mode, all 4 error correction levels)

Developer Tools

• JSON formatter/validator (pretty-print, minify, error line/column)
• JSON / YAML / XML / CSV converter (convert between any two formats)
• Regex tester with live match highlighting
• Diff viewer (line-level LCS diff)
• Base64 encoder/decoder (UTF-8 safe, optional URL-safe alphabet)
• JWT decoder (decodes header/payload only — does not verify the signature)
• Cron expression parser (plain-language summary + next run times)
• Hash generator (SHA-1/256/384/512 via native Web Crypto)
• RSA key pair generator (2048/3072/4096-bit, signing or encryption, PEM output, via native Web Crypto)
• Bcrypt hash generator / verifier (adjustable salt rounds, via bcryptjs)
• URL encoder/decoder (component and full-URI modes)
• Unix timestamp converter (seconds/milliseconds ⇄ date)
• HTML entity encoder/decoder

Cheatsheets

• Git cheatsheet (searchable reference)
• Bash cheatsheet (searchable reference)
• Regex cheatsheet (searchable reference)
• Excel cheatsheet (searchable reference)
• SQL cheatsheet (searchable reference, MySQL/PostgreSQL/SQLite/SQL Server differences noted)

This is the beginning of the README. Read the rest at the original. Read the full README ↗