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IP Subnet Calculator

Calculate network ranges, subnet masks, usable hosts, and split subnets. 100% client-side — works offline.

/
Common:
IP Address
192.168.1.100
Class C · Private (RFC 1918)
Network Address
192.168.1.0
192.168.1.0/24
Broadcast Address
192.168.1.255
All host bits = 1
Subnet Mask
255.255.255.0
/24
Wildcard Mask
0.0.0.255
Inverse of subnet mask
First Host
192.168.1.1
Lowest usable
Last Host
192.168.1.254
Highest usable
Total Addresses
256
2^8
Usable Hosts
254
Excludes network + broadcast
IP Class
Class C
192.0.0.0 – 223.255.255.255

🔢 Binary Representation

IP:11000000.10101000.00000001.01100100
Mask:11111111.11111111.11111111.00000000
Network:11000000.10101000.00000001.00000000
Cyan bits = network portion (24 bits) · Gray bits = host portion (8 bits)

✂️ Split Subnet

New prefix will be /26
#Subnet (CIDR)Range
1192.168.1.0/26192.168.1.0 – 192.168.1.63
2192.168.1.64/26192.168.1.64 – 192.168.1.127
3192.168.1.128/26192.168.1.128 – 192.168.1.191
4192.168.1.192/26192.168.1.192 – 192.168.1.255
🔒 100% private: All calculations happen in your browser. Your IP data never leaves your device.

About IP Subnet Calculator

Subnetting is the practice of dividing a large IP network into smaller logical subnets. It is foundational for network engineering, firewall rules, routing tables, VPN configuration, and cloud VPC design. Given an IPv4 address and CIDR prefix (like 192.168.1.100/24), a subnet calculator tells you: the network address, broadcast address, subnet mask, wildcard mask, usable host range, and total/usable host counts. It also shows the binary representation, which is essential for understanding how subnetting works and for CCNA/CCNP exam preparation. This tool handles all CIDR prefixes from /0 to /32, plus subnet splitting.

How It Works

  1. Enter an IPv4 address in the IP field (e.g., 192.168.1.100).
  2. Choose or type the CIDR prefix (0–32) or subnet mask.
  3. The tool calculates the network address, broadcast address, host range, and counts instantly.
  4. Use the "Split Subnets" section to divide the network into smaller subnets.

✨ Key Features

  • ✓CIDR prefix from /0 to /32
  • ✓Network and broadcast address calculation
  • ✓Subnet mask and wildcard mask (in dotted decimal)
  • ✓First and last usable host IP
  • ✓Total addresses and usable host count
  • ✓IP class detection (A, B, C, D, E)
  • ✓Private/public IP detection (RFC 1918)
  • ✓Binary representation of address and mask
  • ✓Subnet splitter (split into N subnets)
  • ✓100% client-side — no data sent to any server

🎯 Common Use Cases

  • →Configuring firewalls, routers, and VPNs
  • →Planning cloud VPC subnets (AWS, GCP, Azure)
  • →Setting up Docker or Kubernetes network ranges
  • →CCNA/CCNP exam preparation and practice
  • →Debugging "host unreachable" or "no route to host" errors
  • →Planning IP allocations for offices and data centers
  • →Verifying subnet overlaps before merging networks
  • →Teaching subnetting concepts to students

💡 Advanced Tips & Pro Insights

  • ▸CIDR notation: /24 = 256 addresses = 254 usable hosts (network and broadcast are reserved). /25 = 128 addresses = 126 hosts. /30 = 4 addresses = 2 hosts (common for point-to-point links).
  • ▸The subnet mask 255.255.255.0 equals /24. Use this tool to convert between dotted-decimal masks and CIDR prefixes.
  • ▸Private IP ranges (RFC 1918): 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16. These are not routable on the public internet.
  • ▸The wildcard mask (inverse of subnet mask) is used in Cisco ACLs and OSPF configurations — e.g., /24 has wildcard 0.0.0.255.
  • ▸For IPv6 subnetting, use a dedicated IPv6 calculator — the math is different (128-bit addresses, /64 is the standard LAN subnet).

Frequently Asked Questions

Is this subnet calculator free?▾
Yes, this IP subnet calculator is completely free with no signup, email, or usage limits.
Is my data safe?▾
Yes, 100% safe. All calculations happen in your browser. Your IP addresses are never sent to any server.
What is CIDR notation?▾
CIDR (Classless Inter-Domain Routing) notation is a compact way to specify an IP network. "192.168.1.0/24" means the first 24 bits are the network portion and the last 8 bits are the host portion. /24 equals a subnet mask of 255.255.255.0.
How do I know the subnet mask for a CIDR prefix?▾
Common examples: /8 = 255.0.0.0, /16 = 255.255.0.0, /24 = 255.255.255.0, /25 = 255.255.255.128, /26 = 255.255.255.192, /30 = 255.255.255.252. This tool shows the mask for any prefix.
Why are 2 addresses unusable per subnet?▾
The first address is the network address (all host bits 0) and the last is the broadcast address (all host bits 1). Neither can be assigned to a host. For /31 (RFC 3021) and /32, special rules apply.
What is a wildcard mask?▾
A wildcard mask is the bitwise inverse of a subnet mask. For /24, the wildcard mask is 0.0.0.255. Cisco ACLs and routing protocols (OSPF, EIGRP) use wildcard masks instead of subnet masks.
How do I know if an IP is private?▾
Private (RFC 1918) ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. This tool automatically detects private/public IPs and shows the result.
What is a /30 subnet used for?▾
A /30 has 4 addresses — 2 usable hosts. It is commonly used for point-to-point WAN links between routers, where only two devices need IPs.