Convert CIDR prefixes to masks, ranges, and host counts — /8 through /32 decoded. Answer 'how many IPs in a /22' instantly — local math, free, no signup.
Compute subnet masks, network/broadcast addresses, and usable host ranges from any CIDR. Plan a /24 office network correctly — local math, free, no signup.
Decode QR codes from uploaded images. Scan any QR code image and extract the embedded text or URL. Point it at screenshots, photos, or documents — decoded URLs and text copy out instantly. Runs locally, free, no signup.
Decode Base64 strings and pretty-print JSON data — paste encoded text to see the decoded result instantly. Inspect API payloads and tokens readably — free, local, no signup.
Compute monthly burn and runway from starting balance, ending balance, and months elapsed. Know exactly how many months remain — free, local, no signup.
Convert numbers between binary, octal, decimal, and hex with bitwise views. Read 0xFF as 255 instantly — local math, free, no signup.
1024 total, 1022 usable (minus network + broadcast). Each prefix bit halves the space: /24→256, /23→512, /22→1024.
255.255.255.224 — 32 usable hosts, the classic small-office or VLAN size. The tool shows mask, wildcard, and binary together.
Adjacent same-size blocks merge: two /24s become one /23 when aligned. Alignment matters — 10.0.1.0/24 + 10.0.2.0/24 merge; .1 + .3 do not.
No — math runs locally in your browser. Nothing leaves your device.
No host subtraction: at prefix 31 and above the total is 2 to the power (32 - prefix), with first = network and last = broadcast (a /31 gives 2 addresses, a /32 gives 1). Below 31 it is 2 to the power (32 - prefix) minus 2, so the default 192.168.1.0/24 reports 254. Prefix must be 0-32 and every octet 0-255.
Subnet Calculator
Compute subnet masks, network/broadcast addresses, and usable host ranges from any CIDR. Plan a /24 office network correctly — local math, free, no signup.
IP Allowlist Generator
Build IP allowlist rules for firewalls, security groups, and app configs from CIDR lists. Generate AWS, Nginx, and htaccess formats — local, free, no signup.
Last updated October 2026