IPv4 Subnet Calculator

What is an IPv4 Subnet Calculator?

An IPv4 subnet calculator computes network boundaries, address ranges, and subnet details from an IP address and CIDR notation. Network administrators use it to plan address allocation, troubleshoot connectivity, and understand how subnets divide IP space.

What It Calculates

Enter an IPv4 address with optional CIDR notation and get:

• Network Address — the subnet identifier (first address)
• Subnet Mask — in dotted decimal and binary format
• Wildcard Mask — inverse of subnet mask (used in ACLs)
• Network Size — total addresses in the subnet
• First/Last Usable Address — range for host assignment
• Broadcast Address — last address in the subnet
• IP Class — classful network designation (A, B, C, D, E)

Key Features

• Real-time calculation as you type
• Supports CIDR notation (/0 to /32)
• Auto-detects appropriate CIDR for private ranges
• Navigate between adjacent subnet blocks
• Shows subnet mask in binary for learning
• Client-side processing — no data sent to servers

How to Use

1. Enter an IPv4 address (e.g., 192.168.1.50)
2. Add CIDR notation for specific subnet size (e.g., /24)
3. Results appear instantly below
4. Use Previous/Next buttons to navigate adjacent blocks
5. Click Reset to clear and start over

Understanding CIDR Notation

CIDR (Classless Inter-Domain Routing) notation specifies how many bits define the network portion of an address:

• /24 — 24 network bits, 8 host bits = 256 addresses (254 usable)
• /16 — 16 network bits, 16 host bits = 65,536 addresses
• /32 — single host (no network range)
• /0 — entire IPv4 space (default route)

Smaller CIDR numbers mean larger networks. Each decrease by 1 doubles the network size.

FAQs

• What if I don’t specify CIDR?
  The calculator auto-assigns based on private address ranges: /8 for 10.x.x.x, /12 for 172.16-31.x.x, /16 for 192.168.x.x, and /24 for others.
• What is the wildcard mask for?
  Wildcard masks are used in router ACLs and OSPF configurations. They’re the inverse of the subnet mask — 0s match, 1s ignore.
• Why are first and last addresses different from network/broadcast?
  Network address identifies the subnet itself; broadcast is for sending to all hosts. Neither can be assigned to a device, so usable range excludes them.
• Is my data secure?
  Yes. All calculations happen in your browser. No IP addresses are transmitted to any server.