Saved
Developer tools·Networking

Subnet / CIDR Calculator

Free IPv4 subnet calculator: enter an IP and CIDR prefix or subnet mask to get network, broadcast, host range, and wildcard mask instantly. No sign-up.

Added Jun 1, 2026

Quick examples

Input

Result

Enter a value for ip address to see your result.

How it works

Calculates IPv4 subnet details from an IP address and CIDR prefix or subnet mask. Returns network and broadcast addresses, usable host range, host count, wildcard mask, and dotted-binary representation — essential for network design, firewall rules, and cloud VPC planning.

Formula

Network = IP AND Mask · Broadcast = Network OR Wildcard

Mask
32-bit value with leading 1s (from CIDR prefix or subnet mask)
Wildcard
Bitwise NOT of the subnet mask (used in ACLs)
Usable hosts
2^(32−prefix) − 2 (except /31 and /32 per RFC 3021)

Step by step

  1. 01Enter an IPv4 address and choose CIDR prefix or subnet mask input.
  2. 02The calculator derives the subnet mask from the prefix (or reads the mask directly).
  3. 03Network address = IP AND mask; broadcast = network OR wildcard (inverted mask).
  4. 04First and last usable hosts exclude network and broadcast (except /31 point-to-point links).

Examples

Home LAN · 192.168.1.100/24

A /24 on 192.168.1.x yields 254 usable hosts — the classic home router subnet.

Inputs

IP address:
192.168.1.100
Subnet input:
cidr
CIDR prefix:
24

Result

Network address:
192.168.1.0
Broadcast address:
192.168.1.255
First usable host:
192.168.1.1
Last usable host:
192.168.1.254
Usable hosts:
254
Subnet mask:
255.255.255.0
CIDR notation:
192.168.1.0/24

Office VLAN · 10.20.30.45/26

A /26 splits a /24 into four subnets of 62 hosts each — common for office VLANs.

Inputs

IP address:
10.20.30.45
Subnet input:
cidr
CIDR prefix:
26

Result

Network address:
10.20.30.0
Broadcast address:
10.20.30.63
First usable host:
10.20.30.1
Last usable host:
10.20.30.62
Usable hosts:
62
CIDR notation:
10.20.30.0/26
Note: The IP address does not need to be the network address — the tool masks it automatically. /31 subnets (RFC 3021) show two usable addresses for point-to-point links; /32 is a single host.

Related guides

Frequently asked questions

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) writes a subnet as an IP address followed by a slash and prefix length — e.g. 192.168.1.0/24. The prefix (24) means the first 24 bits are the network portion; the remaining 8 bits are available for hosts.

What is a wildcard mask?

A wildcard mask is the bitwise inverse of the subnet mask. It is used in Cisco ACLs and some firewall rules to match address ranges. For a /24 subnet, the subnet mask is 255.255.255.0 and the wildcard mask is 0.0.0.255.

How many usable hosts are in a /24 subnet?

A /24 has 256 total addresses. Subtracting the network address (.0) and broadcast address (.255) leaves 254 usable host addresses — the most common size for a small LAN.

What is the difference between subnet mask and CIDR?

They represent the same thing in different formats. CIDR /24 equals subnet mask 255.255.255.0 — both mean 24 leading network bits. CIDR is compact; dotted-decimal masks are common in router configs.