IP Subnet Calculator
Calculate network address, broadcast address, subnet mask, and usable host range from an IP and CIDR prefix.
192.168.1.0
Network address
192.168.1.255
Broadcast address
255.255.255.0
Subnet mask
192.168.1.1
First usable host
192.168.1.254
Last usable host
254
Usable hosts
Free to use, no sign-up, no limit on how many times you run it.More developer tools
Overview
A standard subnetting reference calculator for network engineers, sysadmins, and anyone configuring IP ranges — computes every key value from just an IP and prefix length.
- Covers network address, broadcast, mask, and usable host range
- Instant results as you adjust the IP or prefix
- Handles edge cases like /31 and /32 correctly
How to use it
- 1Enter an IPv4 address
- 2Adjust the CIDR prefix slider
- 3Read the calculated subnet details
Frequently asked questions
What does the CIDR prefix mean?
It's the number of bits used for the network portion of the address — a /24 means the first 24 bits are fixed (the network), leaving 8 bits for host addresses.
Why are usable hosts 2 fewer than the total?
The first address in a subnet is reserved as the network address and the last as the broadcast address, so neither can be assigned to a device — except in /31 and /32 subnets, which use special rules.