How this calculator works
- Step 1Read the prefix/24The first bits name the network; the rest name hosts.
- Step 2Keep the network bits192.168.1.0All host bits set to 0.
- Step 3Fill the host bits192.168.1.255All host bits set to 1: the broadcast address.
An IPv4 address is 32 bits. The prefix says how many of them, from the left, identify the network. The remaining bits number the hosts inside it.
Worked example: a home network
192.168.1.10/24 sits in 192.168.1.0/24, which has 254 usable addresses.
- Network
address AND mask- Broadcast
network OR wildcard
- Address in binary11000000.10101000.00000001.00001010
- Mask in binary11111111.11111111.11111111.00000000
- Network192.168.1.0
- Broadcast192.168.1.255
- Usable hosts: 2^8 − 2254
Reading the result
- /30 and shorterTotal − 2 hostsThe first address is the network and the last is broadcast.
- /31 links2 hostsPoint-to-point links use both addresses (RFC 3021).
- Private10/8, 172.16/12 and 192.168/16, for internal networks.
- Carrier-grade NAT100.64/10, used by ISPs that share one public address among customers.
- DocumentationRanges reserved for examples, never on the internet.
- Loopback and multicast127/8 and 224/4 are special.
Related networking and number tools
Subnetting is binary arithmetic on addresses. Other tools help with the numbers and the network around it.
To check masks and addresses bit by bit, use the binary calculator or the hex calculator. For transfer times over a link, the bandwidth calculator handles GB vs GiB and Mbps vs MB/s.
Common mistakes
Mistake: Giving a host the network or broadcast address.
Instead: Use only the host range shown.
Mistake: Using a mask such as 255.0.255.0.
Instead: Masks must be ones followed by zeros.
Mistake: Treating a 100.64.x.x address as public.
Instead: It is shared carrier space; you are behind your ISP’s NAT.
Read how we test our calculators, or browse more developer tools.