IP Subnet Calculator · Practical guide
How to Find the Network and Broadcast Address
AND the IP with its mask to get the network address; set the host bits to 1 for the broadcast.
At a glance
The Two-Step Method
To find the network address, bitwise-AND the IP address with the subnet mask — this zeroes out the host bits. To find the broadcast address, take the network address and set every host bit to 1 (equivalently, OR the network address with the wildcard mask). The calculator above performs both operations for any IPv4 address and CIDR prefix instantly.
Interactive tool
IP Subnet Calculator
Enter your own values, then compare the result with the examples below.
Subnet Details
Worked Example: 192.168.1.137/26
A /26 mask is 255.255.255.192, leaving 6 host bits. The last octet of the IP is 137, and 137 in binary starts with bits 10 — so it falls in the block that begins at 128:
- Network address: 192.168.1.128 (137 AND 192 = 128)
- Broadcast address: 192.168.1.191 (128 + 63, since 6 host bits give 64 addresses)
- Usable host range: 192.168.1.129 – 192.168.1.190 (62 hosts)
Anchor Blocks Make It Fast
The network address is always a multiple of the block size. For a /26, the last octet's blocks are 0, 64, 128, and 192 — so any IP from .128 to .191 belongs to 192.168.1.128/26. To find the network for any prefix, divide the relevant octet by the block size, round down, and multiply back.
Why These Two Addresses Matter
Routers use the network address to build routing tables — "everything in 192.168.1.128/26 goes out this interface." The broadcast address reaches every host on the subnet at once, used by protocols like ARP and DHCP. Because both are spoken for, neither can be assigned to a device, which is why a subnet always has two fewer usable addresses than its total.
Frequently Asked Questions
What is the network address of 10.1.5.200/24?
10.1.5.0. A /24 mask keeps the first three octets and zeroes the last. The broadcast is 10.1.5.255, with usable hosts from 10.1.5.1 to 10.1.5.254.
Is the broadcast address always the .255 address?
No — only for /24 networks. For a /26, broadcasts end in 63, 127, 191, or 255. The broadcast is always the last address of the subnet's block, whatever the prefix.
Can two different IPs share the same network address?
Yes, and that's the point. Every host in 192.168.1.0/26, from .1 to .62, reports the network address 192.168.1.0 — that's what puts them on the same subnet.
What happens on /31 point-to-point links?
There is no broadcast address. Per RFC 3021, both addresses in a /31 are usable host addresses, since a link with exactly two endpoints never needs to broadcast.