IP Subnet Calculator

Enter any IPv4 address and CIDR prefix to instantly calculate the network address, subnet mask, wildcard, broadcast, host range and binary breakdown.

IPv4 / CIDR Input
/
Common:
Network Address / CIDR —
Subnet Mask —
Wildcard Mask —
Broadcast Address —
IP Class / Scope —
First Usable Host —
Last Usable Host —
Usable Hosts —
Total Addresses —
Binary Breakdown
Network bits
Host bits
CIDR Reference Table
Prefix Subnet Mask Addresses Usable Hosts
/8255.0.0.016,777,21616,777,214
/16255.255.0.065,53665,534
/20255.255.240.04,0964,094
/22255.255.252.01,0241,022
/23255.255.254.0512510
/24255.255.255.0256254
/25255.255.255.128128126
/26255.255.255.1926462
/27255.255.255.2243230
/28255.255.255.2401614
/29255.255.255.24886
/30255.255.255.25242
/31255.255.255.25422 (P2P)
/32255.255.255.25511 (Host)

How to use the IP Subnet Calculator

Enter any IPv4 address in dotted-decimal notation (e.g. 192.168.1.100) and set the CIDR prefix length (0–32). All subnet values update instantly. Use the quick-prefix buttons to switch between the most common subnet sizes.

What each field means

Binary breakdown explained

The binary panel shows the IP address and subnet mask in 32-bit binary. Network bits (purple) are the fixed portion shared by all hosts in the subnet. Host bits (teal) are the variable portion used to address individual hosts.

Frequently asked questions

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) expresses an IP address and its network prefix as a single string — for example 192.168.1.0/24. The number after the slash tells you how many bits belong to the network portion. CIDR replaced the older classful system (Class A/B/C) in 1993, allowing far more flexible address allocation.

How many usable hosts does a /24 subnet have?

A /24 subnet contains 256 total addresses (2^8). Two are reserved — the network address and the broadcast address — leaving 254 usable hosts. In general, usable hosts = 2^(32 - prefix) - 2 for prefixes shorter than /31.

What is the difference between subnet mask and wildcard mask?

The subnet mask uses 1s to mark network bits (e.g. 255.255.255.0 = 11111111.11111111.11111111.00000000). The wildcard mask is its bitwise complement — it uses 1s for host bits (e.g. 0.0.0.255). Wildcard masks are standard in Cisco IOS access control lists and OSPF network statements.

What are the private IP address ranges?

RFC 1918 defines three private ranges not routable on the public internet: 10.0.0.0/8 (Class A — up to 16M hosts), 172.16.0.0/12 (Class B — up to 1M hosts), and 192.168.0.0/16 (Class C — up to 65K hosts). Devices on private networks access the internet through NAT.