IP Subnet Calculator Online Free Tool
IP Subnet Calculator
IPv4 Configuration
Format: xxx.xxx.xxx.xxx
Range: /0 to /32
An IP subnet calculator takes an IP address and subnet mask (or CIDR notation) and computes the network address, broadcast address, usable host range, and number of hosts. Understanding subnetting is essential for network design, security, and troubleshooting.
See also:
Understanding IP Subnetting
An IPv4 address is 32 bits, written as four decimal octets (e.g., 192.168.1.0). A subnet mask defines which bits identify the network and which identify the host. CIDR notation (/24) indicates how many bits are the network portion.
CIDR /24 → 24 network bits, 8 host bits Subnet Mask: 11111111.11111111.11111111.00000000 = 255.255.255.0 Hosts per subnet = 2^(host bits) - 2 /24 → 2^8 - 2 = 254 usable hosts (subtract network address and broadcast address) Network Address = IP AND Subnet Mask Broadcast = Network Address OR NOT(Subnet Mask)
Example: 192.168.1.100/24 → Network: 192.168.1.0, Broadcast: 192.168.1.255, Hosts: .1-.254
Common Subnet Sizes
| CIDR | Subnet Mask | Hosts per Subnet |
|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 |
| /16 | 255.255.0.0 | 65,534 |
| /24 | 255.255.255.0 | 254 |
| /25 | 255.255.255.128 | 126 |
| /28 | 255.255.255.240 | 14 |
| /30 | 255.255.255.252 | 2 |
Frequently Asked Questions
What are private IP address ranges?⌄
RFC 1918 designates three private ranges not routed on the public internet: 10.0.0.0/8 (10.x.x.x), 172.16.0.0/12 (172.16-31.x.x), and 192.168.0.0/16 (192.168.x.x). Home and office networks use these ranges. NAT (Network Address Translation) maps private IPs to one or more public IPs at the router.
What is the difference between IPv4 and IPv6?⌄
IPv4 uses 32-bit addresses (about 4.3 billion unique addresses). IPv6 uses 128-bit addresses (about 3.4 × 10^38 addresses). IPv4 exhaustion drove IPv6 adoption. IPv6 addresses are written as 8 groups of 4 hex digits: 2001:0db8:85a3::8a2e:0370:7334. IPv6 includes built-in features for auto-configuration and security.
Why do we need subnetting?⌄
Subnetting divides a large network into smaller subnetworks for security, performance, and management. It isolates broadcast domains (too many devices on one network creates traffic congestion). It enables access control between departments. It efficiently allocates address space without wasting large blocks on small groups.
What is a default gateway?⌄
The default gateway is the IP address of the router that handles traffic to destinations outside the local subnet. When a device wants to communicate with an IP address not on its local network, it sends the traffic to the default gateway, which routes it appropriately. Typically the gateway is the first or last usable host address in a subnet (like 192.168.1.1).