IP Subnet CIDR Calculator
Resolve broadcast ranges, wildcards, netmasks, and usable IP limits from a CIDR notation.
Subnet Details
| IP Address | 192.168.1.1 |
| Network Address | 192.168.1.0 |
| Usable Host Range | 192.168.1.1 — 192.168.1.254 |
| Broadcast Address | 192.168.1.255 |
| Subnet Mask | 255.255.255.0 |
| Wildcard Mask | 0.0.0.255 |
| Total Usable Hosts | 254 |
| Binary Mask | 00000000.00000000.000000-1.00000000 |
What is this tool?
The CIDR Subnet Calculator analyzes IPv4 addresses and Classless Inter-Domain Routing (CIDR) prefixes to calculate network boundaries, broadcast addresses, wildcard masks, and usable host address ranges. It provides instant visual breakdowns of bitmask allocations and RFC 1918 network classifications.
How to calculate IPv4 subnets and CIDR masks
- Enter a valid IPv4 address (e.g., 192.168.1.1) in the IP Address field.
- Select or slide the CIDR prefix length between /0 and /32.
- Examine the calculated subnet mask, wildcard mask, network address, and broadcast address.
- Review the usable host address range and binary subnet bit visualization.
Key Features
- Calculates subnet mask, wildcard mask, network ID, and broadcast address
- Computes first usable, last usable, and total usable host capacity
- Handles special point-to-point (/31) and single-host (/32) subnet allocations
- Identifies RFC 1918 private address ranges vs public routable blocks
- Displays binary bit allocation across network and host portions
Frequently Asked Questions
What does CIDR notation represent?
CIDR (Classless Inter-Domain Routing) notation specifies an IP address followed by a slash and the prefix length (e.g., /24), indicating how many leading bits represent the network prefix.
Why are two addresses subtracted from the total host count?
In standard IPv4 subnets (/30 and larger), the first address is reserved as the network identifier and the final address is reserved for subnet broadcasts, leaving 2^(32 - prefix) - 2 addresses for usable hosts.
How does a /31 subnet work for point-to-point links?
Under RFC 3021, /31 subnets have only 2 addresses and omit dedicated network and broadcast addresses, allowing both IPs to be used on router-to-router point-to-point links without wasting address space.
What is a wildcard mask?
A wildcard mask is the bitwise inverse of a subnet mask, commonly used in Cisco Access Control Lists (ACLs) and OSPF routing configurations to define address match criteria.
Privacy First
All IP address calculations occur locally in your browser. No network queries or IP logs are made.