Tool
Free Subnet Calculator Online – CIDR & IP Range
Calculate network addresses, broadcast addresses, subnet masks, usable host ranges, and CIDR notation — all locally in your browser.
Subnet Calculator
Berechne Subnetz-Informationen aus IP und CIDR
How Subnetting Works
Every IPv4 address consists of 32 bits, divided into a network portion and a host portion. The subnet mask determines where the boundary falls. For example, a subnet mask of 255.255.255.0 (or /24 in CIDR notation) means the first 24 bits identify the network and the remaining 8 bits identify individual hosts within that network. By adjusting this boundary, you can create subnets of different sizes to match your requirements.
CIDR Notation Explained
CIDR notation replaced the old classful addressing system (Class A, B, C) with a more flexible approach. Instead of being limited to /8, /16, or /24 boundaries, CIDR allows any prefix length from /0 to /32. The number after the slash indicates how many bits of the address are used for the network portion. A smaller prefix number means a larger network: /16 contains 65,536 addresses while /28 contains only 16.
Common Subnet Masks
/8 (255.0.0.0) — 16.7 million hosts, used for large enterprise networks. /16 (255.255.0.0) — 65,534 hosts, common for campus networks. /24 (255.255.255.0) — 254 hosts, the most common LAN subnet. /28 (255.255.255.240) — 14 hosts, used for small server segments. /30 (255.255.255.252) — 2 hosts, standard for point-to-point links. /32 (255.255.255.255) — single host, used for loopback and host routes.
Frequently Asked Questions
- What is subnetting?
- Subnetting is the process of dividing a larger IP network into smaller, more manageable sub-networks (subnets). It improves network performance, enhances security through isolation, and makes more efficient use of available IP address space.
- What is CIDR notation?
- CIDR (Classless Inter-Domain Routing) notation represents an IP address and its subnet mask in a compact format: the IP address followed by a slash and the number of network bits. For example, 192.168.1.0/24 means the first 24 bits define the network, leaving 8 bits (256 addresses) for hosts.
- What is the difference between network address and broadcast address?
- The network address is the first address in a subnet (all host bits set to 0) and identifies the network itself. The broadcast address is the last address (all host bits set to 1) and is used to send data to all hosts in the subnet. Neither can be assigned to individual devices.
- How many usable hosts does a /24 subnet have?
- A /24 subnet has 256 total addresses (2^8), but 2 are reserved: the network address and broadcast address. So there are 254 usable host addresses. Similarly, a /28 has 16 total addresses and 14 usable hosts.
- Does this calculator work offline?
- Yes. All subnet calculations happen locally in your browser using JavaScript. No data is sent to any server, so the tool works even without an internet connection once the page is loaded.