Ipv4 Subnet Calculator

Free online tool. All processing is client-side. No signup needed.

How to Use the Ipv4 Subnet Calculator

1. Enter your input values above
2. Results update automatically
3. Copy or download the output

What is a Ipv4 Subnet Calculator?

An IPv4 Subnet Calculator computes network parameters from an IP address and subnet mask or CIDR notation — network address, broadcast address, usable host range, number of hosts, and wildcard mask. Subnetting is a fundamental skill in networking: dividing a larger network into smaller sub-networks for better organization, security, and efficient IP address use. Network engineers, system administrators, and DevOps engineers use subnet calculations daily when configuring servers, firewalls, VPNs, and cloud VPCs.

How Does It Work?

Enter an IP address and either a subnet mask (255.255.255.0) or CIDR prefix (/24). The calculator performs bitwise AND between the IP and mask to get the Network Address, and sets all host bits to 1 to get the Broadcast Address. Usable hosts = 2^(32−prefix) − 2 (subtracting network and broadcast addresses). The results show both binary and decimal representations for learning.

Formula

Network Address = IP AND Subnet Mask (bitwise AND)\nBroadcast = Network OR Wildcard Mask (bitwise OR)\n\nWildcard Mask = NOT Subnet Mask (bitwise NOT)\n\nTotal Addresses = 2^(32 − CIDR Prefix)\nUsable Hosts = 2^(32 − Prefix) − 2\n\nSubnet Mask (decimal) = sum of bits set × 2^(8×(3−octet_index))\n\nCIDR Notation: /N where N = number of consecutive 1 bits in the mask\n\nCommon Subnets:\n/8  = 255.0.0.0 (16,777,214 hosts)\n/16 = 255.255.0.0 (65,534 hosts)\n/24 = 255.255.255.0 (254 hosts)

Who Uses This Tool?

• Network engineers designing IP addressing schemes for corporate networks
• System administrators configuring server subnets, firewalls, and routing
• Cloud engineers planning VPC CIDR blocks in AWS, Azure, or GCP
• DevOps engineers setting up Docker or Kubernetes pod networks
• Students learning subnetting for networking certifications (CCNA, Network+)

Pro Tips

• Remember the −2 rule for usable hosts: network address (.0) and broadcast address (.255 in /24) are reserved and can't be assigned to devices
• For cloud VPCs, the cloud provider reserves additional IPs: AWS reserves 5 IPs per subnet (first 4 + last 1), so a /28 (16 total) only has 11 usable
• Plan for growth: allocate larger subnets than you currently need. A /24 (254 hosts) seems generous but can fill up fast with containers and microservices
• Avoid overlapping subnets when connecting networks via VPN. Plan all subnets from a single supernet to prevent conflicts

Frequently Asked Questions about Ipv4 Subnet Calculator

What's the difference between /24 and 255.255.255.0?

They're the same thing. /24 is CIDR notation — it means the first 24 bits are the network portion (255.255.255.0 in decimal). /24 is shorter and preferred in modern networking.

Why can't I use the first and last IP in a subnet?

The first IP is the network address (identifies the subnet itself) and the last is the broadcast address (used to send packets to ALL devices on that subnet). Neither can be assigned to a specific device.

Free online Ipv4 Subnet Calculator — no signup, 100% client-side processing. All data stays in your browser.