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IP Subnet Calculator

Free CIDR notation calculator for network subnetting

💡 Quick Tip: Enter an IP address with CIDR notation (e.g., 192.168.1.0/24) to instantly calculate network details. Use preset buttons for common networks!
Common Networks
IP Address
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Subnet Mask
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Network Address
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Broadcast Address
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Usable IP Range
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Total IP Addresses
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Usable IP Addresses
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IP Class
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Wildcard Mask
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IP Binary
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Mask Binary
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Network Binary
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Broadcast Binary
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Network Address (UInt32)
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Subnet Mask (UInt32)
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Broadcast Address (UInt32)
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Why Use This Subnet Calculator?

Frequently Asked Questions

1. What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation is a compact representation of IP addresses and their associated routing prefix. The format is IP/prefix, where the prefix indicates how many bits form the network address (e.g., 192.168.1.0/24 means the first 24 bits define the network).

2. What's the difference between network and broadcast address?

The network address is the first address in a subnet (all host bits set to 0) and identifies the entire network. The broadcast address is the last address (all host bits set to 1) and is used to send messages to all devices on that network.

3. What is a subnet mask?

A subnet mask is a 32-bit number that masks an IP address and divides it into network and host portions. It uses 1s for the network portion and 0s for the host portion. For example, 255.255.255.0 masks the first three octets as the network.

4. What is a wildcard mask and when do I use it?

A wildcard mask is the inverse of a subnet mask (0s become 1s and vice versa). It's commonly used in Access Control Lists (ACLs) on routers and firewalls to define which IP addresses or portions of addresses should match a condition. For example, wildcard 0.0.0.255 matches any address in that final octet.

5. How many usable IPs are in a /24 network?

A /24 network has 256 total addresses (2^8). Subtracting the network and broadcast addresses, you get 254 usable IP addresses for hosts. The /24 is equivalent to the traditional Class C subnet mask 255.255.255.0.

6. What are private IP ranges?

Private IP ranges (RFC 1918) are reserved for internal use and not routable on the public internet: 10.0.0.0/8 (10.0.0.0 - 10.255.255.255), 172.16.0.0/12 (172.16.0.0 - 172.31.255.255), and 192.168.0.0/16 (192.168.0.0 - 192.168.255.255).

7. What is the binary representation used for?

Binary representation shows how IP addresses and subnet masks are stored at the bit level. This is useful for understanding subnetting logic, troubleshooting network issues, and verifying calculations. Each octet is converted to 8 binary digits (bits).

8. What is UInt32 format and why do I need it?

UInt32 (32-bit unsigned integer) is a hexadecimal representation of IP addresses used in programming and API calls. For example, 192.168.1.0 becomes 0xC0A80100. This format is commonly used in code when dealing with IP address manipulation at the binary level.