Why is total hosts 254 for /24 and not 256?

The first address in a subnet is the network address and the last is the broadcast — neither can be assigned to a host. So a /24 has 256 total addresses but only 254 usable hosts.

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CIDR Calculator

Enter a CIDR like 192.168.1.0/24 — get the network address, broadcast, netmask, wildcard mask, host range, and total usable hosts. Works for any IPv4 prefix from /0 to /32. Browser-only, no upload.

IP input

CIDR notation

IPv4 address

Prefix length: /24

Results

IP converter

Network

—

Broadcast

—

Usable hosts

—

Status

Ready

Example

CIDR cheat sheet

The number after the slash is the count of leading 1 bits in the netmask. Bigger prefix = smaller subnet.

192.168.1.0/24

Network:    192.168.1.0
Broadcast:  192.168.1.255
Netmask:    255.255.255.0
Wildcard:   0.0.0.255
First host: 192.168.1.1
Last host:  192.168.1.254
Hosts:      254 usable (256 total)

Common prefixes

/8   16,777,214 hosts  255.0.0.0
/16  65,534 hosts      255.255.0.0
/24  254 hosts         255.255.255.0
/26  62 hosts          255.255.255.192
/28  14 hosts          255.255.255.240
/30  2 hosts           255.255.255.252
/32  1 host (point)    255.255.255.255

Use cases

What you'll use this for

UUIDs are the universal "give me a unique identifier" tool — no central coordination required.

Subnet planning

Size a subnet to the host count you need without over-allocating address space.

Firewall rules

Find the network and broadcast for your ACL entries; verify a host lives in the expected subnet.

Cloud VPCs

AWS, GCP, Azure all want CIDRs for VPCs and subnets. Validate splits before deploying.

Routing tables

Confirm aggregation: does 10.0.0.0/8 cover the supernet you think it does?

Step by step

How to use the CIDR calculator

Paste a CIDR

Type 192.168.1.0/24 in the CIDR field — or set the IP and prefix separately.

Drag the prefix slider

Watch network size change in real time. /24 = 254 hosts, /16 = 65,534, /8 = 16M.

Read results

Network, broadcast, mask, wildcard, host range — every value updates as you type.

Copy values

Click any value to copy it. Use Copy results to grab all of them as a labelled list.

FAQ

Frequently asked questions

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) writes a subnet as ip/prefix where the prefix is the number of leading 1 bits in the netmask. 192.168.1.0/24 means the first 24 bits are the network and the last 8 are host bits.

Why is total hosts 254 for /24, not 256?

The first address is the network address (192.168.1.0) and the last is the broadcast (192.168.1.255). Neither can be assigned to a host, so 256 total addresses → 254 usable.

What about /31 and /32?

RFC 3021 allows /31 for point-to-point links (both addresses usable, no broadcast). /32 is a single host.

What's a wildcard mask?

The bitwise complement of the netmask: 0.0.0.255 for /24. Cisco ACLs and OSPF use wildcard masks instead of netmasks.

Is it free?

Yes. No signup, no limits, no ads. Calculation happens entirely in your browser.

About

About CIDR notation

CIDR (RFC 4632) replaced class-based addressing in 1993. Subnets are now specified by an explicit prefix length rather than implied by the address.

How the calculation works

Netmask — 0xFFFFFFFF << (32 - prefix).
Network — ip AND netmask.
Broadcast — network OR ~netmask.
Usable hosts — 2^(32-prefix) − 2 (or 2 for /31, 1 for /32).

Common subnets

/30 — point-to-point WAN links (2 hosts).
/29 — small WAN segments (6 hosts).
/24 — typical office LAN (254 hosts).
/16 — large campus or AWS VPC (65,534 hosts).
/8 — RFC 1918 private space 10.0.0.0/8.