Subnet Calculator

Calculate subnet masks, network addresses, broadcast addresses, and host ranges for IPv4 and IPv6 CIDR blocks.

Security & Privacy

This tool is being rebuilt

The earlier version did not work as described, so it is switched off until a tested version replaces it at this same address.

Tell us what you need it for

Tools that work today

IP ACL Builder Who gets in, by address, with no surprises.
IP Range Merger & Optimizer Merge overlapping IP ranges, aggregate CIDR blocks, and minimize firewall rules. Supports allow/deny list optimization.
IP Header Decoder Decode IPv4 and IPv6 packet headers from hex dumps. Visualize fields: version, TTL, protocol, source/destination.
MAC Address Lookup & Generator Look up MAC address vendor (OUI) information. Generate random MAC addresses with optional vendor prefix.
Network Bandwidth Calculator Calculate data transfer times, bandwidth requirements, and throughput. Convert between Mbps, MB/s, and transfer durations.
Network Latency Tester Measure round-trip latency to endpoints using fetch timing API. Graph latency over time and compute statistics.

Web app by bee2.io

SCOUTb2

Website quality scanner

A Chrome extension that crawls a website and reports the accessibility, performance, and search problems it finds, page by page, with a shareable...

Open SCOUTb2

Mac app by bee2.io

HearthKeeper

Private home inventory

Catalogs a whole home room by room with photos, receipt scanning, and barcodes, then exports the record locally.

More Security & Privacy tools

CVSS Score Calculator Vector strings scored exactly by the spec.
OpenPGP Key Lookup Every field read from the key itself.
CVE Lookup One CVE, every field explained.
Breached Password Check Only five characters of a hash ever leave.
VPN Leak Check What a website really sees behind your VPN.
Password Generator Random done right, with the maths shown.

What is it about?

What's missing Something isn't working Could be better Another tool I need Other

Your message (required)

0 / 2000 characters, at least 10

Name (optional)

Email (optional, for a reply)

Leave this field empty

Sent with your message: the address of this page, b2kit.com/tools/ipv4-ipv6-subnet-calculator/

Pressing Send gives your message and this page's address to bee2.io, the team behind b2KIT. Your name and email go along only if you enter them, and any reply goes to that email. How we handle feedback

Sent. Thank you.

This tool is being rebuilt

Help improve this tool Tell us what is missing, broken or worth adding. One minute.