What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation represents an IP address and its associated routing prefix. It is written as an IP address followed by a slash and the prefix length, for example 192.168.1.0/24. The number after the slash indicates how many bits are used for the network portion of the address.

What is a subnet mask?

A subnet mask is a 32-bit number that divides an IP address into network and host portions. It is written in dotted-decimal notation (e.g. 255.255.255.0) where consecutive 1s mark the network bits and 0s mark the host bits. It is equivalent to a CIDR prefix — 255.255.255.0 equals /24.

How many hosts are in a /24 network?

A /24 network has 256 total addresses (2^8). Two are reserved — the network address (first) and broadcast address (last) — leaving 254 usable host addresses.

What is the difference between network address and broadcast address?

The network address is the first IP in a subnet (all host bits set to 0) and identifies the subnet itself. The broadcast address is the last IP (all host bits set to 1) and is used to send packets to every host on that subnet. Neither can be assigned to individual hosts.

What are private IP address ranges?

Private IP ranges are reserved for internal networks and are not routable on the public internet. They are: 10.0.0.0/8 (Class A), 172.16.0.0/12 (Class B), and 192.168.0.0/16 (Class C). The loopback range 127.0.0.0/8 is also non-routable.

What is a wildcard mask?

A wildcard mask is the inverse of a subnet mask, calculated by subtracting each octet from 255. For example, the wildcard of 255.255.255.0 is 0.0.0.255. Wildcard masks are used in access control lists (ACLs) on routers and firewalls to specify IP ranges.

What is subnet splitting?

Subnet splitting (subnetting) divides a larger network into smaller equal-sized subnets by borrowing bits from the host portion. For example, splitting a /24 into 4 subnets yields four /26 networks, each with 62 usable hosts. This is useful for organising network segments.

What do /31 and /32 subnets mean?

A /32 is a host route — it represents a single IP address with no network or broadcast. A /31 (per RFC 3021) contains exactly 2 addresses and is used for point-to-point links; both addresses are usable as hosts with no broadcast address.

IP Subnet Calculator

Calculate IP subnets, host ranges, and network details from CIDR

Updated Mar 2026100% Private — runs in browser

CIDR Address

Subnet Details

IP Address

192.168.1.0

Subnet Mask

255.255.255.0 (/24)

Network Address

192.168.1.0

Broadcast Address

192.168.1.255

First Host

192.168.1.1

Last Host

192.168.1.254

Total Hosts

256

Usable Hosts

254

IP Class

Class C

IP Type

Private

Wildcard Mask

0.0.0.255

CIDR Notation

192.168.1.0/24

Binary Representation

Binary IP Address

11000000.10101000.00000001.00000000

Binary Subnet Mask

11111111.11111111.11111111.00000000

Network bits (24)Host bits (8)

Common Subnet Reference

CIDR	Subnet Mask	Usable Hosts	Use
/8	255.0.0.0	16,777,214	Use
/16	255.255.0.0	65,534	Use
/24	255.255.255.0	254	Use
/25	255.255.255.128	126	Use
/26	255.255.255.192	62	Use
/27	255.255.255.224	30	Use
/28	255.255.255.240	14	Use
/30	255.255.255.252	2	Use

Click any row to apply that subnet to the calculator above.