IPv4 CIDR Subnet Calculator
Enter any IPv4 address and CIDR prefix (`/8` to `/32`) to calculate the network ID, dotted-decimal subnet mask, wildcard mask, broadcast address, and usable host IP range.
How to Read IPv4 Subnet Calculator Results
Every IPv4 subnet divides a 32-bit address into two portions: the Network Prefix (the leading bits locked by the CIDR mask, such as the first 24 bits in a /24 network) and the Host Identifier (the remaining trailing bits assigned to individual devices). In standard networks (`/8` through `/30`), two addresses in every block are reserved by protocol design and cannot be assigned to computers or routers:
- Network ID (First Address): All host bits are set to
0(e.g.,192.168.1.0in192.168.1.0/24). Identifies the route itself in routing tables. - Usable Host Range: Runs from
Network ID + 1throughBroadcast - 1(e.g.,192.168.1.1to192.168.1.254). Usually,.1or.254is assigned to the Default Gateway router. - Broadcast Address (Last Address): All host bits are set to
1(e.g.,192.168.1.255). Packets sent here are delivered to every interface on that local broadcast domain.
Common Small Office & Home LAN CIDR Reference Table
| CIDR Prefix | Subnet Mask | Wildcard Mask | Total IPs | Usable Hosts | Typical Use Case |
|---|---|---|---|---|---|
/32 | 255.255.255.255 | 0.0.0.0 | 1 | 1 (Single Host) | Firewall host rule / Loopback / WireGuard peer |
/30 | 255.255.255.252 | 0.0.0.3 | 4 | 2 | Point-to-point router-to-router WAN/VPN link |
/29 | 255.255.255.248 | 0.0.0.7 | 8 | 6 | Business static WAN IP block (5 usable + 1 gateway) |
/28 | 255.255.255.240 | 0.0.0.15 | 16 | 14 | Small isolated management or NVR camera VLAN |
/26 | 255.255.255.192 | 0.0.0.63 | 64 | 62 | Departmental VoIP phone or IoT device VLAN |
/24 | 255.255.255.0 | 0.0.0.255 | 256 | 254 | Standard home & small office LAN subnet |
/23 | 255.255.254.0 | 0.0.1.255 | 512 | 510 | Growing office or guest WiFi network |
/22 | 255.255.252.0 | 0.0.3.255 | 1,024 | 1,022 | Large mesh network (default on Amazon eero) |
RFC 1918 Private IPv4 Ranges for Local Networks
When designing internal VLANs or changing your router's LAN subnet to avoid VPN collisions (since 192.168.1.0/24 and 192.168.0.0/24 frequently collide with remote coffee-shop or hotel networks), always pick addresses inside the three IANA-reserved RFC 1918 private blocks:
- Class A Private Block:
10.0.0.0/8(10.0.0.0–10.255.255.255) — Ideal for clean VLAN numbering such as10.10.20.0/24for VLAN 20. - Class B Private Block:
172.16.0.0/12(172.16.0.0–172.31.255.255) — Great for WireGuard/OpenVPN tunnel subnets that rarely overlap with home routers. - Class C Private Block:
192.168.0.0/16(192.168.0.0–192.168.255.255) — Used by default on consumer routers; pick an uncommon third octet like192.168.45.0/24if hosting a VPN server.