Why does a /24 have 254 usable hosts rather than 256?

A /24 contains 256 addresses, but the first is the network address and the last is the broadcast address, and neither can be assigned to a host — leaving 254. This does not apply at /31 or /32, which the tool handles separately.

How do I tell whether an address is private?

RFC 1918 defines 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 as private. The tool states this directly, and also flags 127.0.0.0/8 loopback and 169.254.0.0/16 link-local addresses. None of the three are routed on the public internet.

NETWORK TOOLS · NO PACKETS ARE SENT

Subnet Calculator (CIDR)

Work out the network address, broadcast, usable host range, and subnet divisions from an IP and prefix.

Input

CIDR

Network address192.168.1.0/24

Usable hosts254

Results

Network address192.168.1.0

Broadcast address192.168.1.255

First usable host192.168.1.1

Last usable host192.168.1.254

Subnet mask255.255.255.0

Wildcard mask0.0.0.255

Total addresses256

Address classC

Binary mask11111111.11111111.11111111.00000000

Address scopePrivate

Divide into subnets

New prefix length

Showing the first 4

Network address	First usable host	Last usable host	Usable hosts
`192.168.1.0/26`	`192.168.1.1`	`192.168.1.62`	`62`
`192.168.1.64/26`	`192.168.1.65`	`192.168.1.126`	`62`
`192.168.1.128/26`	`192.168.1.129`	`192.168.1.190`	`62`
`192.168.1.192/26`	`192.168.1.193`	`192.168.1.254`	`62`

About this tool

Enter an IP and CIDR prefix such as 192.168.1.10/24 to get the network address, broadcast address, first and last usable host, subnet mask, wildcard mask, total addresses, and usable hosts, along with whether the address is private, loopback, or link-local. You can also divide the block into smaller subnets and list each range. Host counts are special at /31 and /32: a /31 is a point-to-point link under RFC 3021 where both addresses are usable, and a /32 is a single host — neither reserves a network and broadcast address.

How it works

Enter an IP and prefix length, or paste CIDR notation.
Read the network, broadcast, usable range, and masks.
To divide the block, enter a longer prefix and read each subnet.

Limits and notes

Address arithmetic only — no packets are sent. /31 and /32 host counts follow RFC 3021.

Privacy

Addresses and strings are calculated inside this browser only. Nothing is uploaded, stored, or written to the URL or any log.

Frequently asked questions

Why does a /24 have 254 usable hosts rather than 256?: A /24 contains 256 addresses, but the first is the network address and the last is the broadcast address, and neither can be assigned to a host — leaving 254. This does not apply at /31 or /32, which the tool handles separately.
How do I tell whether an address is private?: RFC 1918 defines 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 as private. The tool states this directly, and also flags 127.0.0.0/8 loopback and 169.254.0.0/16 link-local addresses. None of the three are routed on the public internet.

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