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Subnet Calculator

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Enter an IP address and CIDR prefix to find the network address, broadcast address, subnet mask, and usable host range.

Subnet Calculator

Live
Network address192.168.1.0
Broadcast address192.168.1.255
Subnet mask255.255.255.0
Usable host range192.168.1.1 - 192.168.1.254
Usable hosts254
Total addresses256
Works with standard IPv4 addresses and CIDR notation.

The method

Subnet mask = CIDR prefix converted to 32 bits (leading 1s, trailing 0s) Network address = IP address AND subnet mask Broadcast address = Network address OR (NOT subnet mask)
Example

192.168.1.0/24: network = 192.168.1.0, broadcast = 192.168.1.255, giving 254 usable host addresses in between.

Step-by-step guide

  1. Enter an IP address (any address within the subnet works).
  2. Enter the CIDR prefix - the number after the slash, like /24.
  3. Read the network details - subnet mask, address range, and host count.

Why a smaller CIDR number means a bigger network

CIDR notation can feel backward at first: a /24 network (256 addresses) is actually smaller than a /16 network (65,536 addresses), even though 24 is a bigger number than 16. That's because the CIDR number counts how many bits are reserved for the network portion of the address - the more bits used for the network, the fewer bits remain for individual hosts, and each remaining bit doubles the address space. This is exactly why /30 (4 addresses) is common for a tiny point-to-point link, while /8 (over 16 million addresses) is reserved for enormous networks.

Common mistakes

Assigning the network or broadcast address to an actual device - both addresses are reserved for network functions and aren't usable as a host address.
Confusing a smaller CIDR number with a smaller network - it's the opposite, since a smaller prefix leaves more bits available for host addresses.

Frequently asked questions

Why does usable hosts equal total addresses minus 2?

The first address in any subnet is reserved as the network address, and the last is reserved as the broadcast address - neither can be assigned to an individual device, leaving the addresses in between as usable.

What's special about a /31 or /32 network?

A /31 has only 2 addresses total and is commonly used for point-to-point links (like between two routers) where both addresses can be used without a separate network/broadcast reservation. A /32 identifies a single specific host.

Does this work for IPv6?

No - this calculator is built specifically for IPv4 addresses and subnetting. IPv6 uses a much larger address space with different conventions.

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