Subnet / CIDR calculator

Enter an IPv4 address with a CIDR prefix (e.g. 10.0.0.0/24) to get the network, broadcast, usable host range, and host count.

How to use the subnet / cidr calculator

  1. Enter an IPv4 address with a CIDR prefix, e.g. 10.0.0.0/24.
  2. Press Calculate.
  3. Read the network, broadcast, host range, and host count.

Reading the results

The CIDR prefix (e.g. /24) says how many leading bits identify the network; the rest address hosts. The network address is the first in the range and the broadcast is the last — neither is assignable to a device, which is why a /24 has 256 total addresses but 254 usable. Calculated entirely in your browser.

Code & API examples

Use this from the command line or your code.

Shell (ipcalc)
ipcalc 10.0.0.0/24
Python
import ipaddress
n = ipaddress.ip_network('10.0.0.0/24')
print(n.network_address, n.broadcast_address, n.num_addresses)

See all endpoints at /api/tools/.

Frequently asked questions

The /24 is the CIDR prefix — it says the first 24 bits are the network portion, leaving 8 bits (254 usable addresses) for hosts.

The network address is the first address in the range (identifies the subnet); the broadcast address is the last (used to reach every host at once). Neither is assignable to a device.
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