About IPv4 Subnet & CIDR Calculator
Comprehensive IPv4 subnet and CIDR mask calculator. Enter any IP and CIDR prefix (e.g. 192.168.1.0/24) to compute network ID, broadcast address, total hosts, usable host range, wildcard mask, binary subnet representation, and RFC 1918 private status.
Key Capabilities & Features
- Complete 32-bit bitwise calculation of network and broadcast addresses
- Total and usable host counts for all prefixes (/1 to /32)
- Subnet mask and inverted Cisco wildcard mask
- 32-bit binary notation breakdown for IP and netmask
- IPv4 address class (A, B, C, D, E) and RFC 1918 private/public determination
How to Use IPv4 Subnet & CIDR Calculator
Enter IP Address
Type an IPv4 address (e.g., 10.0.0.1 or 192.168.1.100).
Select CIDR Prefix
Choose your subnet mask from the dropdown or slider (/8 to /30).
Review Subnet Specs
Examine network ID, usable host range, broadcast address, and binary breakdown.
Privacy & In-Browser Execution Guarantee
Runs 100% client-side. Calculations are computed using 32-bit bitwise math in browser memory.
Frequently Asked Questions
What is CIDR notation in IPv4 networking?
Classless Inter-Domain Routing (CIDR) notation (e.g., /24) specifies how many leading bits of an IP address represent the network prefix, leaving the remaining bits for host addresses.
How do I calculate the number of usable hosts in an IPv4 subnet?
The formula is 2^(32 - prefix) - 2. We subtract two addresses because the first address represents the Network Identifier and the last address is the Broadcast Address.
What is a wildcard mask and where is it used?
A wildcard mask is the bitwise inverse of a subnet mask (e.g., 0.0.0.255 for a 255.255.255.0 subnet). It is widely used in Cisco IOS Access Control Lists (ACLs) and OSPF routing configurations.