Subnet Calculator
Calculate subnet with our free tool. Get data-driven results, visualizations, and actionable recommendations. Enter your values for instant results.
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
Network Address = IP AND Subnet Mask; Broadcast = Network OR Wildcard Mask
The network address is found by performing a bitwise AND between the IP address and subnet mask. The broadcast address is found by performing a bitwise OR between the network address and the wildcard mask (inverse of subnet mask). Usable hosts = 2^(32-CIDR) - 2 (subtracting network and broadcast addresses). The CIDR prefix length indicates how many leading bits form the network portion.
Worked Examples
Example 1: Standard Home Network (/24)
Problem:Calculate subnet details for IP 192.168.1.100 with CIDR /24.
Solution:IP: 192.168.1.100\nCIDR: /24 → Subnet Mask: 255.255.255.0\n\nBinary IP: 11000000.10101000.00000001.01100100\nBinary Mask: 11111111.11111111.11111111.00000000\n\nNetwork (AND): 11000000.10101000.00000001.00000000 = 192.168.1.0\nBroadcast (OR wildcard): 192.168.1.255\nWildcard: 0.0.0.255\n\nUsable range: 192.168.1.1 - 192.168.1.254\nTotal hosts: 256, Usable: 254
Result:Network: 192.168.1.0 | Range: .1-.254 | Broadcast: .255 | 254 usable hosts
Example 2: Enterprise Subnet (/26)
Problem:Subnet 10.0.5.67/26 — find the network, broadcast, and usable range.
Solution:IP: 10.0.5.67\nCIDR: /26 → Subnet Mask: 255.255.255.192\nWildcard: 0.0.0.63\n\n67 in binary: 01000011\nMask last octet: 11000000\nAND: 01000000 = 64\n\nNetwork: 10.0.5.64\nBroadcast: 10.0.5.64 + 63 = 10.0.5.127\nFirst host: 10.0.5.65\nLast host: 10.0.5.126\nUsable hosts: 62
Result:Network: 10.0.5.64 | Range: .65-.126 | Broadcast: .127 | 62 usable hosts
Frequently Asked Questions
How do I determine the right subnet size for my network?
To choose the right subnet size, count the number of devices that need IP addresses and select a CIDR prefix that provides enough usable addresses with room for growth. Include all devices: computers, phones, printers, IoT devices, network equipment, and servers. Plan for 50-100% growth beyond current needs. For 10 devices: /28 gives 14 usable addresses. For 25 devices: /27 gives 30 usable addresses. For 50 devices: /26 gives 62 usable addresses. For 100 devices: /25 gives 126 usable addresses. For 200 devices: /24 gives 254 usable addresses. Remember that every subnet loses 2 addresses (network and broadcast), and you may need addresses for the default gateway, DHCP server, DNS server, and other infrastructure. A common mistake is choosing a subnet that exactly matches current needs — always leave headroom. For VLANs in enterprise networks, /24 is the most common choice for general-purpose subnets.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy