CIDR Block
Split a Network
IP ↔ Binary Breakdown
Route Summarisation / Supernet
Instantly compute IP ranges, subnet masks, split networks, visualise binary, and summarise routes.
Six client-side calculations covering subnetting, splitting, and route summarisation — nothing you type leaves your browser.
Enter any CIDR block or bare IP to instantly get the network address, broadcast address, usable host range, subnet mask, wildcard mask, and total/usable host counts.
Break a parent block into smaller, equally-sized subnets at any new prefix length — useful for planning VLANs, allocating address space across sites, or sizing a new network.
See exactly which bits make up the network portion versus the host portion of an address, with the network/host boundary clearly marked — built for teaching and for sanity-checking masks by eye.
Feed in a list of IPs or CIDR blocks and find the smallest single block that covers all of them — handy for collapsing static routes, ACLs, or firewall rules into one summary entry.
Recognises private (RFC 1918), loopback, link-local, multicast, and other reserved ranges so you can spot whether a block is routable on the public internet at a glance.
All math happens client-side in JavaScript — nothing you type is sent to a server, logged, or stored. Safe to use against real internal address plans.
A /24 network contains 256 IP addresses, of which 254 are usable for hosts — the first address is the network address and the last is the broadcast address.
CIDR (Classless Inter-Domain Routing) notation writes an IP address followed by a slash and the number of network bits, for example 192.168.1.0/24. The prefix length says how many leading bits identify the network; the remaining bits are available for hosts.
A subnet mask marks the network bits as 1s, such as 255.255.255.0 for a /24. A wildcard mask is its inverse, 0.0.0.255, and is used in ACLs and OSPF to indicate which bits are allowed to vary.
Choose a longer prefix than the parent block. Splitting a /22 into /24s, for example, yields four equal /24 subnets. The Subnet Splitter tab lists every resulting block automatically.
Yes. Every calculation runs entirely in your browser in JavaScript — nothing you enter is sent to a server, logged, or stored, so it is safe to use with real internal address plans.