Calculate IPv4 subnets from CIDR notation. Get network address, broadcast address, host range, wildcard mask, and usable host count — all instantly in your browser.
IP/Subnet Calculator is a free tool that computes IPv4 subnet details from any IP address with CIDR notation. Enter an address like 192.168.1.0/24 and instantly get the network address, broadcast address, subnet mask, wildcard mask, host range, and total usable hosts. It also identifies the IP class and whether the address is in a private range — essential information for network planning and infrastructure design.
Use this calculator when planning network segments, configuring routers and firewalls, setting up VPCs in cloud environments, or troubleshooting connectivity issues. It is especially useful for DevOps engineers working with infrastructure-as-code, network administrators designing subnet layouts, and anyone who needs to quickly verify CIDR ranges without manual binary math.
Network engineers use this tool to plan IP address allocation for office networks and data centers, calculate subnet sizes for VLANs, determine wildcard masks for Cisco ACL configurations, verify that IP ranges do not overlap in multi-subnet environments, and quickly convert between CIDR notation and dotted decimal subnet masks during troubleshooting sessions.
Essential terms and definitions related to IP/Subnet Calculator.
A 32-bit number that divides an IP address into network and host portions. The mask has consecutive 1-bits for the network part and 0-bits for the host part. For example, /24 equals 255.255.255.0 — the first 24 bits identify the network and the remaining 8 bits identify hosts within that network.
The inverse of a subnet mask, used primarily in Cisco ACLs and OSPF configurations. It is calculated by subtracting the subnet mask from 255.255.255.255. For a /24 network (subnet mask 255.255.255.0), the wildcard mask is 0.0.0.255, indicating that the last octet can vary.
A method for allocating IP addresses that replaced the old classful (Class A/B/C) system. CIDR uses variable-length subnet masking (VLSM) allowing networks to be divided into subnets of any size, reducing IP address waste and enabling more efficient routing table aggregation.
CIDR (Classless Inter-Domain Routing) notation represents an IP address and its associated network prefix. For example, 192.168.1.0/24 means the first 24 bits define the network, leaving 8 bits for host addresses. The number after the slash is the prefix length, which determines the subnet mask and the number of available hosts.
A /24 subnet has 256 total addresses (2^8), but 2 are reserved: the network address (first) and the broadcast address (last). This gives 254 usable host addresses. The formula is: usable hosts = 2^(32 - prefix) - 2.
The network address is the first address in a subnet and identifies the network itself — it cannot be assigned to a host. The broadcast address is the last address and is used to send packets to all hosts on the subnet. Both are reserved and reduce the usable host count by 2.
Yes. This tool works with any valid IPv4 address including private ranges: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. These are the most common ranges for internal network planning and home lab setups.
Common errors developers encounter and how to resolve them.
Invalid IP address format Ensure the IP address contains exactly four octets separated by dots, with each octet being a number between 0 and 255. Examples: 192.168.1.0, 10.0.0.0. Leading zeros are not standard (use 10 not 010).
CIDR prefix out of range The CIDR prefix must be between 0 and 32 for IPv4. Common values: /8 (Class A), /16 (Class B), /24 (Class C), /32 (single host). Values outside this range are invalid.
Unexpected calculation results for edge cases For /31 subnets (point-to-point links, RFC 3021), there are 2 addresses and 0 usable hosts in traditional calculation, though modern routers use both. For /32, it represents a single host address. These are valid but special cases.