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CIDR Subnet Calculator

Calculate IPv4 network configurations, subnet masks, host address boundaries, wildcards, and binary IP masks from CIDR blocks instantly. Enter your IP and CIDR prefix to inspect netmask parameters locally in the browser.

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Learn About This Tool

Understanding IP subnetting and CIDR blocks

CIDR (Classless Inter-Domain Routing) notation represents an IP address paired with a routing prefix (e.g. /24). The prefix number defines how many bits are locked for the network portion, with the remaining bits allocated for host addresses. If you are mapping database systems containing network logs or API inputs, try our JSON Formatter & Validator. Here is a standard `/24` subnet mapping:
# CIDR Notation: 192.168.1.1/24

Netmask Address    : 255.255.255.0
Network Address    : 192.168.1.0
Broadcast Address  : 192.168.1.255
Usable Host Range  : 192.168.1.1 - 192.168.1.254
Total Usable Hosts : 254
  • Subnet Mask defines which portion of the IP is network vs host
  • Network Address forms the starting identifier of the subnet
  • Broadcast Address defines the target for sending data to all hosts
  • Usable Host Range shows the assignable client IPs inside the subnet

Binary mask representations and wildcard calculations

Network routers and firewalls process IPs in binary (32 bits) and use wildcard masks (inverse netmasks) for routing configurations. Our calculator displays the binary values for the IP address, Netmask, and Network boundaries side-by-side. If you are managing text-based server configurations, parse them using our Duplicate Line Remover.
  • Wildcard mask is calculated by inverting the netmask (e.g. 0.0.0.255 for /24)
  • Binary views display bits in 8-bit octet blocks separated by periods
  • Calculates the total host bounds including unusable addresses (network & broadcast)
  • Helps parse CIDR ranges when writing firewall and security rules

Secure offline calculations for server protection

Inputting corporate network IP schemas (such as private subnets or server gateways) into web tools can disclose internal network architectures. Our CIDR calculator compiles network parameters 100% inside client-side JavaScript. Your IP configurations are never transmitted.
  • Secures internal IP addresses by running calculations locally in browser memory
  • Maintains absolute privacy for system configurations and network structures
  • Runs instantly without loading delays or server round-trip times
  • Allows copying results immediately for configs, scripts, or documentation

How to Use CIDR Subnet Calculator

1

Enter your IPv4 address

Type your base IP address (e.g. 192.168.1.1) in the text input. The validator checks the octet ranges (0-255) dynamically.

2

Select your CIDR prefix block

Choose the CIDR network prefix (from /0 to /32) using the dropdown selector. This determines the netmask boundaries.

3

Inspect your network parameters

The calculated parameters (Subnet, Broadcast, Wildcard, Host counts, and Binary octets) display instantly in the output panel.

Code Implementations

Copy & paste production-ready code snippets for CIDR Subnet Calculator in your language of choice

File: cidr_calc.py
Python
import ipaddress

net = ipaddress.ip_network('192.168.1.0/24')

print("Network Address:  ", net.network_address)
print("Broadcast Address:", net.broadcast_address)
print("Netmask:          ", net.netmask)
print("Total Hosts:      ", net.num_addresses)
print("Usable Hosts:     ", net.num_addresses - 2)

Frequently Asked Questions

Enter your base IP address and choose the CIDR network prefix (e.g. /24) in the dropdown. The tool instantly computes the subnet mask, network start, broadcast end, and usable IP host range.
CIDR (Classless Inter-Domain Routing) notation specifies an IP address and its associated routing prefix length (e.g. 192.168.1.1/24), indicating that 24 bits are allocated for the network prefix.
A subnet mask is a 32-bit number that splits an IP address into network and host addresses. For a /24 CIDR prefix, the subnet mask is 255.255.255.0.
A /24 subnet has a total of 256 host addresses. Subtracting 2 (one for the network address, and one for the broadcast address) leaves 254 usable host IPs.
Yes, 100%. All subnet math is calculated locally in your browser using JavaScript. No IP addresses or network details are ever uploaded to any server.
A wildcard mask is the bitwise inversion of the subnet mask, commonly used in Cisco OSPF and access control lists (ACLs). For netmask 255.255.255.0, the wildcard mask is 0.0.0.255.
The network address is calculated using a bitwise AND between the IP and the mask. The broadcast address is calculated by performing a bitwise OR between the IP and the inverted mask.
Currently, our subnet calculator supports IPv4 address blocks, which are the most common configurations for local networks and routing tables.
Yes. You can copy individual fields like the host range or wildcard mask directly from the output results card.
A /28 CIDR block corresponds to a subnet mask of 255.255.255.240, allowing for 14 usable hosts.
It converts each octet of the IP, netmask, and network addresses into 8-bit binary strings, displaying them in aligned sections to visualize the network/host boundary.
Yes. If an entered IP does not follow the standard x.y.z.w format or has octet values outside 0-255, the validator flags a syntax error.
Total hosts include all combinations of the host bits. Usable hosts exclude the first address (Network ID) and the last address (Broadcast ID) which are reserved for routing.
A /32 prefix designates a single, specific host address (subnet mask 255.255.255.255) with 0 usable client host ranges.
Yes. Once loaded, all binary conversions and mask calculations work offline since they run completely in local client-side memory.

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