IPv4 & IPv6 Subnet Calculator
Calculate network subnets, CIDR prefix lengths, netmasks, broadcast addresses, wildcard masks, and usable host count ranges for IPv4 and IPv6 network allocations.
Subnet Calculation Parameters
Input an IPv4 or IPv6 address and select a CIDR prefix length to compute subnet details, host ranges, and binary representations.
Understanding Classless Inter-Domain Routing (CIDR)
CIDR (Classless Inter-Domain Routing) notation (RFC 4632) replaced traditional Class A, B, and C IPv4 network classes with flexible prefix lengths represented as a forward slash followed by a bit length (such as /24 or /64).
IPv4 Common Subnet Reference Table
| CIDR Prefix | Subnet Mask | Total IP Count | Usable Host IPs |
|---|---|---|---|
/24 | 255.255.255.0 | 256 | 254 |
/26 | 255.255.255.192 | 64 | 62 |
/28 | 255.255.255.240 | 16 | 14 |
/30 | 255.255.255.252 | 4 | 2 (Point-to-Point Link) |
IPv6 Subnetting & Prefix Allocation Rules
IPv6 addresses consist of 128 bits written as 8 groups of 4 hexadecimal digits. Standard RIR allocations and enterprise deployments use the following prefix splits (RFC 4291):
/32: Standard Regional Internet Registry (RIR) allocation to Internet Service Providers./48: Standard enterprise site allocation containing 65,536/64subnets./56: Standard small business or residential customer assignment containing 256/64subnets./64: Standard single LAN subnet prefix length required for SLAAC (Stateless Address Autoconfiguration).