IPv4 Subnet Calculator
Free online IPv4 subnet calculator. Enter an IP and CIDR to instantly get the network address, broadcast address, subnet mask, wildcard mask, host range and host count. Supports subnet division.
What is an IPv4 subnet calculator?
An IPv4 subnet calculator is a tool that computes network information from an IP address and CIDR prefix. It returns the network address, broadcast address, subnet mask, wildcard mask, host range, and the number of usable hosts for a given subnet.
How does the subnet calculator work?
Enter an IPv4 address (e.g. 192.168.1.10) and a prefix length (e.g. /24). The tool applies bitwise operations between the IP and the mask to derive the network and broadcast addresses, then computes the host range and host count entirely in your browser.
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation appends a slash and a prefix length to an IP address, for example 192.168.1.0/24. The number after the slash indicates how many leading bits belong to the network portion of the address.
What is a subnet mask?
A subnet mask is a 32-bit value that separates the network and host portions of an IPv4 address. A /24 mask equals 255.255.255.0, meaning the first 24 bits identify the network and the remaining 8 bits identify hosts.
What is the difference between network address and broadcast address?
The network address is the first address of 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 data to all hosts in the subnet. Neither can be assigned to an individual device.
How many usable hosts are in a /24 network?
A /24 network has 256 total addresses (2^8). After excluding the network address and broadcast address, 254 usable host addresses remain. This is why a typical home network with 192.168.1.0/24 supports 254 devices.
What are the private IP address ranges?
RFC 1918 defines three private IPv4 ranges reserved for internal use: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. These addresses are not routable on the public internet and are used in home and corporate networks.
What is a /31 subnet used for?
A /31 subnet provides only 2 addresses. Per RFC 3021, /31 networks are used for point-to-point links between routers, where both addresses are assigned to the two endpoints, eliminating the need for a dedicated network and broadcast address.
How do I divide a network into subnets?
To divide a network, increase the prefix length. For example, splitting 192.168.1.0/24 into two equal subnets produces 192.168.1.0/25 and 192.168.1.128/25. Each additional bit doubles the number of subnets and halves the size of each one.
What is a wildcard mask?
A wildcard mask is the bitwise inverse of a subnet mask. For a /24 mask (255.255.255.0), the wildcard mask is 0.0.0.255. Wildcard masks are commonly used in access control lists (ACLs) and OSPF configuration on Cisco routers.
How are IP address classes determined?
IPv4 addresses are historically divided into classes: Class A (1.0.0.0-126.255.255.255), Class B (128.0.0.0-191.255.255.255), Class C (192.0.0.0-223.255.255.255), Class D (224.0.0.0-239.255.255.255, multicast), and Class E (240.0.0.0-255.255.255.255, experimental). Modern routing uses CIDR instead of fixed classes.
Is my data sent to a server?
No, all subnet calculations are performed locally in your browser using JavaScript. Your IP addresses and network information never leave your device, ensuring complete privacy.
How to Use IPv4 Subnet Calculator
Calculate IPv4 subnets instantly in your browser: network address, broadcast, mask, host range and more. Nothing is sent anywhere — all math runs locally.
- Enter a full address like 192.168.1.100/24 into the CIDR Notation field.
- Prefer splitting it up? Type the IP 192.168.1.100 and the mask /24 into the separate boxes.
- Read the network address, broadcast address, subnet mask and wildcard mask at a glance.
- Check the usable host range and the total number of hosts the subnet supports.
- Open Subnet Division to slice the network into smaller subnets.
- Use the CIDR Quick Reference table whenever you need to decode a prefix length.
Remember that the network and broadcast addresses are not usable, so a /24 effectively offers 254 hosts.
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