What is a CIDR subnet mask?

CIDR (Classless Inter-Domain Routing) defines the network boundary; for example, a /24 prefix corresponds to a subnet mask of 255.255.255.0, meaning the first three octets are fixed as the network portion.

How many usable hosts are in a /24 subnet?

A /24 subnet provides exactly 254 usable hosts (2^8 - 2), excluding the reserved network ID and broadcast address.

Can I assign an IP address outside the calculated range?

No; devices must share the same subnet mask to route directly, meaning the assigned IP must fall strictly between the first and last usable hosts shown in the results.

Why does a /31 or /32 subnet show zero usable hosts?

Standard routing reserves both ends of the range; a /32 is a single host route, while a /31 is typically used for point-to-point links where traditional host addressing is bypassed.

IP Subnet Calculator

IPv4 only: computes network address, broadcast address, and usable host range from an IP and CIDR prefix.

IP Address

CIDR Prefix

Network Address: N/A

Subnet Mask: N/A

Broadcast Address: N/A

First Usable Host: N/A

Last Usable Host: N/A

Usable Host Count: N/A

Instant IPv4 Subnet Verification

Built specifically for network engineers and sysadmins who need instant, precise verification of IPv4 address allocations without opening a CLI terminal or complex spreadsheet. This live IPv4 subnet calculator provides a comprehensive breakdown of any given IP address and CIDR prefix.

Simply input your target IPv4 address and its corresponding CIDR prefix to instantly compute the network address, subnet mask, broadcast address, and the precise range of usable host IP addresses.

How to Use This Tool

Type your target IPv4 address (e.g., 192.168.1.10) into the first field.
Enter the corresponding CIDR prefix length (e.g., 24) into the second field.
View the complete subnet breakdown below, including network boundaries and valid host availability.

FAQ

Q: What is a CIDR subnet mask?: A: CIDR (Classless Inter-Domain Routing) defines the network boundary; for example, a /24 prefix corresponds to a subnet mask of 255.255.255.0, meaning the first three octets are fixed as the network portion.
Q: How many usable hosts are in a /24 subnet?: A: A /24 subnet provides exactly 254 usable hosts (2^8 - 2), excluding the reserved network ID and broadcast address.
Q: Can I assign an IP address outside the calculated range?: A: No; devices must share the same subnet mask to route directly, meaning the assigned IP must fall strictly between the first and last usable hosts shown in the results.
Q: Why does a /31 or /32 subnet show zero usable hosts?: A: Standard routing reserves both ends of the range; a /32 is a single host route, while a /31 is typically used for point-to-point links where traditional host addressing is bypassed.