Network Subnet Calculator

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Network Subnet Calculator

Calculate IP ranges, masks, and host capacities instantly.

/32 (255.255.255.255 – 1 Host) /31 (255.255.255.254 – 2 Hosts) /30 (255.255.255.252 – 4 Hosts) /29 (255.255.255.248 – 8 Hosts) /28 (255.255.255.240 – 16 Hosts) /27 (255.255.255.224 – 32 Hosts) /26 (255.255.255.192 – 64 Hosts) /25 (255.255.255.128 – 128 Hosts) /24 (255.255.255.0 – 256 Hosts) /23 (255.255.254.0 – 512 Hosts) /22 (255.255.252.0 – 1024 Hosts) /21 (255.255.248.0 – 2048 Hosts) /20 (255.255.240.0 – 4096 Hosts) /19 (255.255.224.0 – 8192 Hosts) /18 (255.255.192.0 – 16384 Hosts) /17 (255.255.128.0 – 32768 Hosts) /16 (255.255.0.0 – 65536 Hosts) /15 (254.0.0.0 – 131072 Hosts) /14 (252.0.0.0 – 262144 Hosts) /13 (248.0.0.0 – 524288 Hosts) /12 (240.0.0.0 – 1048576 Hosts) /11 (224.0.0.0 – 2097152 Hosts) /10 (192.0.0.0 – 4194304 Hosts) /9 (128.0.0.0 – 8388608 Hosts) /8 (255.0.0.0 – 16777216 Hosts)
Network Address
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Broadcast Address
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Usable Host Range
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Subnet Mask
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Wildcard Mask
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Total Hosts
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Usable Hosts
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Binary Mask
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Understanding Network Subnetting

A network subnet calculator is an essential tool for system administrators and network engineers. It helps divide an IP network into smaller, manageable sub-networks (subnets). Subnetting improves network performance, security, and organization by isolating traffic and reducing broadcast domains.

Key Terms to Know

  • IP Address: A unique numerical identifier for a device on a network (IPv4 consists of four octets).
  • Subnet Mask: A 32-bit number used to distinguish between the network portion and the host portion of an IP address.
  • CIDR (Classless Inter-Domain Routing): A shorthand notation for subnet masks (e.g., /24 instead of 255.255.255.0).
  • Broadcast Address: The last IP address in a range, used to send data to all devices in that specific subnet.
  • Network Address: The first IP address in a range, used to identify the network itself.

Example Calculation

If you have an IP of 192.168.1.0 with a /24 mask:

Network: 192.168.1.0
Mask: 255.255.255.0
First Usable Host: 192.168.1.1
Last Usable Host: 192.168.1.254
Broadcast: 192.168.1.255
Total Usable Hosts: 254

Why Subnetting Matters

Without subnetting, all devices in a large organization would be on one massive network. This leads to excessive "noise" or broadcast traffic, where every device hears everyone else's status updates, slowing down the entire system. Subnetting creates logical boundaries, ensuring that HR computers don't flood the Engineering department's bandwidth.

function ipToLong(ip) { var parts = ip.split('.'); if (parts.length !== 4) return null; var longValue = 0; for (var i = 0; i < 4; i++) { var octet = parseInt(parts[i]); if (isNaN(octet) || octet 255) return null; longValue = (longValue <>> 0); } function longToIp(long) { return [ (long >>> 24) & 255, (long >>> 16) & 255, (long >>> 8) & 255, long & 255 ].join('.'); } function calculateSubnet() { var ipInput = document.getElementById('ipAddress').value.trim(); var cidr = parseInt(document.getElementById('cidrMask').value); var errorBox = document.getElementById('error-box'); var resultsBox = document.getElementById('results'); errorBox.style.display = 'none'; var ipLong = ipToLong(ipInput); if (ipLong === null) { errorBox.textContent = "Please enter a valid IPv4 address (e.g., 192.168.1.1)."; errorBox.style.display = 'block'; resultsBox.style.display = 'none'; return; } // Mask Calculation var maskLong = 0; if (cidr > 0) { maskLong = (0xFFFFFFFF <>> 0; } else { maskLong = 0; } var wildcardLong = (~maskLong) >>> 0; var networkLong = (ipLong & maskLong) >>> 0; var broadcastLong = (networkLong | wildcardLong) >>> 0; // Display results document.getElementById('resNetwork').innerText = longToIp(networkLong); document.getElementById('resBroadcast').innerText = longToIp(broadcastLong); document.getElementById('resSubnet').innerText = longToIp(maskLong); document.getElementById('resWildcard').innerText = longToIp(wildcardLong); // Host Calculation var totalHosts = Math.pow(2, (32 – cidr)); var usableHosts = (cidr >= 31) ? 0 : (totalHosts – 2); document.getElementById('resTotalHosts').innerText = totalHosts.toLocaleString(); document.getElementById('resUsableHosts').innerText = (usableHosts >> 0).toString(2).padStart(32, '0'); var binaryFormatted = binaryStr.match(/.{1,8}/g).join('.'); document.getElementById('resBinary').innerText = binaryFormatted; resultsBox.style.display = 'grid'; }

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