Calculate Subnet Mask From CIDR Notation
Your network admin gave you 192.168.1.0/24. What does the /24 mean? How many devices can connect? Let's break down subnetting.
Quick Answer
CIDR /24 means a subnet mask of 255.255.255.0 with 254 usable hosts. Use the free subnet calculator at dotsapps.com to instantly see the mask, host count, and IP range for any CIDR.
What CIDR Notation Means
CIDR stands for Classless Inter-Domain Routing. The number after the slash tells you how many bits are used for the network portion of the address.
A /24 means the first 24 bits are the network. The remaining 8 bits are for hosts. Since 8 bits give you 256 values (0-255), and you lose 2 (network and broadcast), you get 254 usable hosts.
Common CIDR values:
- /8 — 16,777,214 hosts (Class A)
- /16 — 65,534 hosts (Class B)
- /24 — 254 hosts (Class C)
- /32 — 1 host (single IP)
How to Convert CIDR to Subnet Mask
The CIDR number tells you how many 1-bits are in the mask. A /24 has 24 ones followed by 8 zeros:
11111111.11111111.11111111.00000000
Convert each group of 8 to decimal: 255.255.255.0
Other common conversions:
- /25 = 255.255.255.128 (126 hosts)
- /26 = 255.255.255.192 (62 hosts)
- /27 = 255.255.255.224 (30 hosts)
- /28 = 255.255.255.240 (14 hosts)
- /30 = 255.255.255.252 (2 hosts)
Finding the Network and Broadcast Address
Every subnet has two reserved addresses. The network address is the first IP (all host bits are 0). The broadcast address is the last IP (all host bits are 1).
For 192.168.1.0/24:
- Network address: 192.168.1.0
- First usable host: 192.168.1.1
- Last usable host: 192.168.1.254
- Broadcast address: 192.168.1.255
You cannot assign the network or broadcast addresses to devices. That is why a /24 has 254 usable IPs, not 256.
When to Use Subnetting in Practice
Subnetting divides a large network into smaller, manageable pieces:
- Security — Isolate departments on different subnets
- Performance — Reduce broadcast traffic on large networks
- Organization — Separate servers, printers, and workstations
- IP conservation — Use only the IPs you need
For example, a small office with 20 devices only needs a /27 (30 usable IPs). Using a /24 (254 IPs) wastes addresses.
How to Do It: Step-by-Step
- 1
Open the Subnet Calculator at dotsapps.com
- 2
Enter an IP address with CIDR (like 192.168.1.0/24)
- 3
See the subnet mask, network address, and broadcast address
- 4
View the usable host range and total host count
- 5
Switch to IPv6 mode for IPv6 subnet calculations
Frequently Asked Questions
What is the subnet mask for /24?
A /24 subnet mask is 255.255.255.0. It provides 254 usable host addresses.
How many usable IPs are in a /28?
A /28 gives you 16 addresses total, but 2 are reserved (network and broadcast). So you get 14 usable host IPs.
What is the difference between /24 and /25?
A /24 has 254 usable hosts and a /25 has 126. Each additional bit in the CIDR cuts the host count roughly in half.
Can I use a /32 subnet?
Yes. A /32 refers to a single IP address. It is used in routing tables and access control lists to specify one exact host.
Does this calculator work for IPv6?
Yes. The tool supports both IPv4 and IPv6 subnet calculations. IPv6 uses larger addresses but the CIDR concept works the same way.
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