IPv4 Subnet Calculator
Enter an IP address in CIDR notation to instantly calculate network address, broadcast, host range, subnet mask, and binary breakdown.
Try:
Network Address
Broadcast Address
Subnet Mask
Wildcard Mask
Usable Hosts
CIDR Prefix
First Usable Host
Last Usable Host
Class & Type
Binary Breakdown
IP Addr
Subnet Mask
Network
Network portion
Host portion
Subnet Reference
CIDR Prefix → Hosts Quick Reference
| Prefix | Subnet Mask | Usable Hosts | Total Addr. | Common Use |
|---|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 | 16,777,216 | Class A / large ISP block |
| /12 | 255.240.0.0 | 1,048,574 | 1,048,576 | RFC 1918 172.16.0.0/12 |
| /16 | 255.255.0.0 | 65,534 | 65,536 | Class B / enterprise campus |
| /20 | 255.255.240.0 | 4,094 | 4,096 | Large datacenter VLAN |
| /22 | 255.255.252.0 | 1,022 | 1,024 | Medium VLAN / building |
| /24 | 255.255.255.0 | 254 | 256 | Standard LAN segment |
| /25 | 255.255.255.128 | 126 | 128 | Half a /24, split LAN |
| /26 | 255.255.255.192 | 62 | 64 | Small VLAN / office floor |
| /27 | 255.255.255.224 | 30 | 32 | Small team / server cluster |
| /28 | 255.255.255.240 | 14 | 16 | Small server subnet |
| /29 | 255.255.255.248 | 6 | 8 | Point-to-point with spares |
| /30 | 255.255.255.252 | 2 | 4 | WAN links, router-to-router |
| /31 | 255.255.255.254 | 2* | 2 | P2P links (RFC 3021) |
| /32 | 255.255.255.255 | 1 | 1 | Host route / loopback |
* /31 per RFC 3021 — both addresses usable, no network/broadcast reservation. Usable hosts = 2^(32−prefix) − 2 for /0–/30.
Binary Example — 192.168.1.0/24
IP Addr
11000000.10101000.00000001.00000000
192.168.1.0
Mask /24
11111111.11111111.11111111.00000000
255.255.255.0
AND →
11000000.10101000.00000001.00000000
192.168.1.0 network
Bcast
11000000.10101000.00000001.11111111
192.168.1.255 (host bits → 1)
Network = IP AND mask. Broadcast = network OR (NOT mask). Blue = network portion (fixed). Green = host portion (variable).
RFC 1918 Private Address Space
10.0.0.0/810.0.0.0 – 10.255.255.255 · 16,777,216 addresses · Class A private172.16.0.0/12172.16.0.0 – 172.31.255.255 · 1,048,576 addresses · Class B private192.168.0.0/16192.168.0.0 – 192.168.255.255 · 65,536 addresses · Class C privateRFC 1918 ranges are not routed on the public internet. Requires NAT (RFC 3022) to reach external destinations.
Understand IPv4 at the packet level
Header fields, fragmentation, TTL, and addressing — all explained.