🌐 IPv4 Subnet Calculator
CIDR Reference
| CIDR | Subnet Mask | Hosts | Common Use |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 | Class A |
| /16 | 255.255.0.0 | 65,534 | Class B |
| /24 | 255.255.255.0 | 254 | Small network |
| /28 | 255.255.255.240 | 14 | VLAN segment |
| /30 | 255.255.255.252 | 2 | Point-to-point |
Frequently Asked Questions
A subnet mask divides an IP address into network and host portions. Written as 255.255.255.0 or in CIDR notation as /24, it tells routers which part of the IP identifies the network and which identifies the specific device.
CIDR (Classless Inter-Domain Routing) notation expresses an IP address and its subnet mask together. /24 means the first 24 bits are the network address — equivalent to 255.255.255.0. /16 = 255.255.0.0, /8 = 255.0.0.0.
A /24 subnet has 256 total addresses (2^8), but 2 are reserved: the network address (first) and broadcast address (last). So a /24 subnet supports 254 usable host addresses.
Private IPs (10.x.x.x, 172.16–31.x.x, 192.168.x.x) are used inside local networks and not routable on the internet. Public IPs are globally unique and assigned by ISPs. NAT (Network Address Translation) allows many private IPs to share one public IP.