🧮 Subnet Calculator
Enter any IPv4 or IPv6 address in CIDR notation — get network address, broadcast, subnet mask, host range, and total addresses instantly.
About Subnet Calculator
This tool calculates all subnet details from any CIDR notation for both IPv4 and IPv6. CIDR (Classless Inter-Domain Routing) notation expresses a network as an IP address and prefix length — e.g. 192.168.0.0/24 means the first 24 bits are the network, leaving 8 bits for hosts (256 total addresses, 254 usable).
For IPv4, the calculator shows: network address, subnet mask (e.g. 255.255.255.0), broadcast address, first and last usable host addresses, and total usable hosts. Common private ranges: 10.0.0.0/8 (16 M addresses), 172.16.0.0/12 (1 M addresses), 192.168.0.0/16 (65 K addresses). Point-to-point links use /30 (2 usable hosts) or /31 per RFC 3021.
For IPv6, there is no broadcast — all addresses in the range are usable. A standard /64 subnet holds 264 ≈ 18 quintillion addresses. A typical ISP allocates a /48 to each customer (65,536 possible /64 subnets). All IPv6 calculations use JavaScript BigInt for full 128-bit precision. Everything runs locally — no data is sent to a server. To identify the type of an individual IPv6 address, see the IPv6 Analyzer.