IP Address Class & Range Calculator
Enter an IPv4 address to determine its class, default subnet mask, usable host range, broadcast address, and number of hosts.
Formulas
Network Address = IP & Subnet Mask (bitwise AND)
Broadcast Address = Network Address | ~Subnet Mask (bitwise OR with inverted mask)
First Usable Host = Network Address + 1
Last Usable Host = Broadcast Address − 1
Total Addresses = 2(32 − CIDR prefix)
Usable Hosts = Total Addresses − 2 (subtract network & broadcast; for /31 and /32 no subtraction)
Assumptions & References
- Applies to IPv4 (32-bit) addresses only.
- Class A: 1.0.0.0 – 126.255.255.255, default mask /8 (16,777,214 usable hosts).
- Class B: 128.0.0.0 – 191.255.255.255, default mask /16 (65,534 usable hosts).
- Class C: 192.0.0.0 – 223.255.255.255, default mask /24 (254 usable hosts).
- Class D: 224.0.0.0 – 239.255.255.255 — Multicast; no standard host mask.
- Class E: 240.0.0.0 – 255.255.255.255 — Reserved / Experimental.
- 127.x.x.x is reserved for loopback (RFC 990).
- Private ranges (RFC 1918): 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
- /31 networks (RFC 3021) support 2 usable hosts (point-to-point links); /32 is a host route.
- Subnet mask must be contiguous (e.g. 255.255.255.0); non-contiguous masks are rejected.
- References: RFC 791 (IPv4), RFC 950 (Subnetting), RFC 1918 (Private Address Space), RFC 3021 (/31 prefixes).