IP Subnet Calculator
Calculate IPv4 subnet details from an IP address and CIDR prefix or subnet mask. See network address, broadcast, host range, wildcard mask, and binary representations.
Subnet Details
/24 — Class CIP Address192.168.1.0
Subnet Mask255.255.255.0
Wildcard Mask0.0.0.255
Network Address192.168.1.0
Broadcast Address192.168.1.255
First Host192.168.1.1
Last Host192.168.1.254
Total Addresses256
Usable Hosts254
Binary Representation
IP Address
11000000.10101000.00000001.00000000
Subnet Mask
11111111.11111111.11111111.00000000
24 network bits + 8 host bits
Common CIDR Reference
| Prefix | Mask | Usable Hosts |
|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 |
| /16 | 255.255.0.0 | 65,534 |
| /20 | 255.255.240.0 | 4,094 |
| /24 | 255.255.255.0 | 254 |
| /25 | 255.255.255.128 | 126 |
| /26 | 255.255.255.192 | 62 |
| /27 | 255.255.255.224 | 30 |
| /28 | 255.255.255.240 | 14 |
| /29 | 255.255.255.248 | 6 |
| /30 | 255.255.255.252 | 2 |
| /31 | 255.255.255.254 | 2 |
| /32 | 255.255.255.255 | 1 |
How to Use IP Subnet Calculator
- 1Enter an IPv4 address or CIDR notation (e.g., 192.168.1.0/24).
- 2Select or type a subnet mask / prefix length.
- 3View calculated network address, broadcast, and host range.
- 4Copy any value or use presets for common subnets.
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What is CIDR notation?▾
CIDR (Classless Inter-Domain Routing) notation represents an IP address and its routing prefix as a single string: IP/prefix-length. For example, 192.168.1.0/24 means the first 24 bits are the network portion and the remaining 8 bits are the host portion. This replaced the older classful networking (Class A/B/C) and allows more flexible allocation of IP address space. /24 ≈ 256 addresses, /16 ≈ 65,536, /8 ≈ 16.7 million.
What is a subnet mask?▾
A subnet mask is a 32-bit number that separates the network portion from the host portion of an IPv4 address. Written in dotted-decimal, a /24 prefix gives mask 255.255.255.0. Bitwise AND of an IP with its mask gives the network address. The complement (inverted mask) is the wildcard mask — used in ACLs (access control lists) in Cisco IOS and Juniper configurations.
What is the network address vs broadcast address?▾
Network address: first address in the subnet (host bits all zero). It identifies the subnet and cannot be assigned to a host. Broadcast address: last address (host bits all one). Packets sent to this address are delivered to all hosts in the subnet. Usable host addresses are everything between these two. A /30 has 4 addresses: 1 network, 2 hosts, 1 broadcast — commonly used for point-to-point links.
How many hosts can fit in a subnet?▾
Usable hosts = 2^(32 - prefix) − 2. The −2 subtracts the network and broadcast addresses. Common sizes: /24 → 254 hosts, /25 → 126, /26 → 62, /27 → 30, /28 → 14, /29 → 6, /30 → 2. Special cases: /31 (2 addresses, no broadcast — RFC 3021 for point-to-point) and /32 (1 address — host route, used for loopbacks and management).
What is a wildcard mask?▾
A wildcard mask is the bitwise inverse of the subnet mask: 0 bits mean "must match", 1 bits mean "any value". For 255.255.255.0 mask, the wildcard is 0.0.0.255. Wildcard masks are used in: Cisco ACLs (access-control lists), OSPF network statements, and firewall rules. Unlike subnet masks (contiguous 1s), wildcard masks can be non-contiguous for matching specific bit patterns.