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IPv4 Subnet & CIDR Calculator

Calculate network boundaries, broadcast addresses, usable host ranges, and binary bit allocations for any IPv4 address and CIDR prefix from /0 to /32.

Quick Definition

An IP Subnet Calculator performs bitwise arithmetic on an IPv4 address and CIDR prefix (such as /24 or /16) to determine the network address, broadcast address, subnet mask, wildcard mask, and the exact range of usable host IP addresses on that network segment.

IPv4 Subnet & CIDR Calculator

IP Address

Subnet Mask / Prefix: /24

/0 (Internet)/16 (Class B)/24 (Class C)/32 (Host)

Quick presets:

CALCULATED NETWORK

192.168.1.0 / 24

254 Usable HostsClass C · Private

Subnet Mask

255.255.255.0

Wildcard Mask

0.0.0.255

Network Address

192.168.1.0

Broadcast Address

192.168.1.255

First Usable Host

192.168.1.1

Last Usable Host

192.168.1.254

Usable Host Range

192.168.1.1 – 192.168.1.254

Total / Usable Hosts

256 (254 usable)

Network Bits: 24 bits (24)Host Bits: 8 bits (2⁸ addresses)

Network IDAvailable Hosts

View Binary Representation & Bitwise Breakdown▾

Metric	Dotted Decimal	32-bit Binary Representation
IP Address	`192.168.1.0`	`11000000.10101000.00000001.00000000`
Subnet Mask	`255.255.255.0`	`11111111.11111111.11111111.00000000`
Network Address	`192.168.1.0`	`11000000.10101000.00000001.00000000`
Broadcast Address	`192.168.1.255`	`11000000.10101000.00000001.11111111`

Common CIDR Subnet Prefix Reference Table

Subnet Mask	Total Addresses	Usable Hosts	Typical Use Case
`255.255.255.255`	1	1	Single Host Route / Loopback
`255.255.255.254`	2	2	RFC 3021 Point-to-Point Links
`255.255.255.252`	4	2	Point-to-Point Router Links
`255.255.255.248`	8	6	Small Branch / Public IP Block
`255.255.255.240`	16	14	Small Office Network
`255.255.255.224`	32	30	Mid-size Department Subnet
`255.255.255.192`	64	62	VLAN Subnet
`255.255.255.128`	128	126	Half Class C Network
`255.255.255.0`	256	254	Standard Class C LAN / Office
`255.255.254.0`	512	510	Multi-Floor Corporate Network
`255.255.252.0`	1,024	1,022	Campus Wireless LAN
`255.255.248.0`	2,048	2,046	Large Campus / Datacenter
`255.255.240.0`	4,096	4,094	Cloud VPC Subnet
`255.255.0.0`	65,536	65,534	Standard Class B / Enterprise VPC
`255.0.0.0`	16,777,216	16,777,214	Class A / ISP Supernet

NETWORK DISCOVERY & INVENTORY

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SUB-NETWORKING GUIDE

How IP Subnetting and CIDR Masks Work

The mathematical principles behind bitwise masks, routing prefixes, and IP allocation strategies.

The Mathematics of Subnetting

An IPv4 address consists of 32 binary bits divided into four 8-bit octets. A subnet mask tells routers which portion of those 32 bits identifies the Network (Subnet ID) and which portion identifies individual Hosts:

Bitwise AND Operation: A router performs a bitwise AND between the destination IP and the subnet mask. If the resulting Network ID matches its routing table, it knows the packet belongs on the local wire.
Network Address: All host bits set to binary 0. Reserved to identify the network.
Broadcast Address: All host bits set to binary 1. Reserved for broadcasting data to all hosts on the subnet.

Practical Real-World Subnetting Examples

Depending on the role of the network segment, different CIDR prefix sizes are selected:

Point-to-Point WAN Links (/30 or /31): Connecting two core routers. A /30 provides 2 usable IPs, while RFC 3021 /31 conserves space by using only 2 IPs total.
Small Branch Office (/24): Provides 254 usable host addresses (e.g., 192.168.1.1 through 192.168.1.254). Ideal for offices with up to 150 employees, reserving room for Wi-Fi devices, printers, and phones.
Corporate Campus / Wi-Fi VLAN (/22): Provides 1,022 usable addresses across 4 contiguous Class C blocks (e.g., 10.0.0.1 through 10.0.3.254). Prevents DHCP scope exhaustion in busy office environments.
Cloud VPC Supernet (/16): Allocates 65,534 IP addresses, typically sliced into multiple /24 subnets distributed across cloud availability zones.

Pro-Tip for Network Architects: Always size subnets for at least 50% future growth to avoid painful IP renumbering projects when new servers or employee workstations are added.

COMMON QUESTIONS

Frequently Asked Questions: Subnets & CIDR

Comprehensive answers on IP calculations, masks, and networking best practices.

What is CIDR notation and why was it introduced?

Classless Inter-Domain Routing (CIDR) notation represents an IP address and its associated routing prefix using a slash followed by a bit count (such as 192.168.1.0/24). Introduced in 1993 (RFC 1519), CIDR replaced the rigid legacy Class A, B, and C allocation scheme, allowing flexible subnet sizing and dramatically slowing IPv4 address exhaustion.

Why does a /24 subnet have 256 total addresses but only 254 usable hosts?

In standard IPv4 subnets, two addresses are reserved by the protocol: the very first address in the block is the Network Address (identifying the wire itself), and the last address is the Broadcast Address (used to transmit packets simultaneously to every host on that subnet). Therefore, usable hosts = 2^(32 - prefix) - 2.

What is an RFC 3021 /31 subnet and where is it used?

Under traditional rules, point-to-point links between two routers required a /30 subnet (4 addresses, 2 usable, wasting 50% of the space). RFC 3021 standardized the use of 31-bit prefixes (/31) specifically for point-to-point links, treating both addresses as usable host endpoints without dedicated network or broadcast addresses.

What is a wildcard mask and how is it used in Cisco / firewall ACLs?

A wildcard mask (or inverse mask) is calculated by inverting the subnet mask (255.255.255.255 minus the subnet mask). For example, a /24 subnet mask of 255.255.255.0 has a wildcard mask of 0.0.0.255. In network access control lists (ACLs) and OSPF routing configurations, binary 0 indicates 'must match exactly' while binary 1 indicates 'wildcard / ignore bit'.

How do I choose the right subnet size for a corporate cloud VPC?

For cloud VPC architectures (AWS, Google Cloud, Azure), engineers typically allocate a /16 block (65,534 addresses) to the overall VPC, and subdivide it into /20 or /24 subnets per availability zone and tier (e.g. public load balancer subnets, private application subnets, and isolated database subnets).

Can Uzvera automatically discover and map devices across my subnets?

Yes. Uzvera provides automated Network Discovery capabilities. By installing the lightweight Uzvera Agent or using SNMP/ARP scanning, Uzvera can sweep your IP subnets to identify connected workstations, Linux servers, switches, and IoT endpoints, displaying their live status in your dashboard.

IPv4 Subnet & CIDR Calculator

192.168.1.0 / 24

Common CIDR Subnet Prefix Reference Table

Discovering and monitoring devices across your subnets?

How IP Subnetting and CIDR Masks Work

The Mathematics of Subnetting

Practical Real-World Subnetting Examples

Frequently Asked Questions: Subnets & CIDR

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