Free, no signup

Enter an address and prefix. See the network instantly.

Works with IPv4 and IPv6. Type an address, pick a prefix, and everything updates live — network address, broadcast/last address, usable range, plus tools to split a network into subnets or list every host in a range.

IPv4

IPv6

IP Address

Prefix

Subnet Mask

Enter a valid address (e.g. 192.168.1.10 or 2001:db8::1)

Bit map (32 bits, 4 octets) network host

Split into subnets (VLSM)

New prefix

Choose a longer prefix than the current one and click Split to divide this network into equal subnets.

List hosts in this range

Click "Show host list" to list every usable address in the current range (capped at 1,000 addresses).

Quick reference — IPv4 CIDR table

The most commonly used prefixes and how many usable addresses each one gives you.

CIDR	Mask	Total addresses	Usable	Typical use

Frequently asked questions

The short version of what most people are actually looking for.

What's the difference between the network address and the broadcast address?

The network address is the first address in an IPv4 subnet (all host bits set to 0) — it identifies the subnet itself and can't be assigned to a device. The broadcast address is the last one (all host bits set to 1) and sends data to every device on that subnet at once. IPv6 doesn't have a broadcast address — multicast is used instead.

Why does usable hosts equal total addresses minus 2?

In IPv4, the first address in a subnet is reserved as the network address and the last as the broadcast address — neither can be assigned to a device. Exceptions: /31 (point-to-point links, both usable) and /32 (a single host route). IPv6 subnets don't reserve addresses the same way.

What does VLSM (splitting into subnets) actually do?

VLSM — Variable Length Subnet Masking — divides one network into several smaller subnets by extending the prefix. For example, a /24 split into /26 subnets gives you 4 equal subnets of 62 usable hosts each, instead of one subnet of 254.

How do I convert a subnet mask to a CIDR prefix?

Count the 1 bits in the mask. 255.255.255.0 has 24 one-bits, so it's /24. Type the mask into the Subnet Mask field and this calculator converts it automatically.