Slash - Subnet Calculator

Paste a CIDR, a bare address, or just a mask and Slash fills in the rest - network, hosts, broadcast, wildcard, hex netmask. Works entirely offline. Free, no sign-in.

An offline subnet calculator for CCNA, Network+, and anyone who works with IP networks day to day.

This is the original Slash - the calculator I built for myself so I could check subnetting in seconds instead of doing the math by hand every time. Type it in or paste it from wherever you copied it; Slash works out the rest, all on-device.

Features:

• Type or paste a CIDR (192.168.1.0/24), a bare address, or a subnet mask - Slash fills in the rest
• Network address, first and last host, broadcast, and where the next subnet starts
• Paste straight from Cisco IOS, ifconfig, or ipconfig output and it pulls the address and mask out for you
• Tap any value to copy it
• "More details" opens the wildcard mask, usable host count, and a bit-by-bit binary view
• Hand it just a mask and get the CIDR prefix, wildcard, and the hex netmask (the ifconfig / route-table style)
• /31 point-to-point (RFC 3021) and /32 handled the way they actually behave
• IPv6 when you need it, light or dark, Recents, optional haptics
• Fully offline. No accounts, ads, tracking, or subscriptions. Free.
• Shamelessly vibe coded using Fable 5; the subnet math lives in its own package and is hand-verified for accuracy

About me: I'm a working network engineer and active CCNA, currently living in the beautifully warm state of Arizona.

Questions, feedback, or a result you can't explain? Email me any time - I'm responsive, and my email actually works.

Privacy: https://tylerdix.com/slash/#privacy

Slash is an independent tool, not affiliated with, endorsed by, or sponsored by Cisco Systems, Inc. or CompTIA, Inc. CCNA and Network+ are trademarks of their respective owners.