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CIDR Calculator

Calculate IPv4 CIDR ranges, subnet sizes, wildcard masks, and usable host boundaries with a fast subnetting workflow.

Live 3 calculations Network Tools Calculator Networking IPv4 Subnetting
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Input

Enter an IPv4 address and a CIDR prefix to calculate subnet boundaries, mask values, and usable host range.

Enter only the numeric prefix, for example 24 for /24.
Reset

Result

Network boundaries, mask values, host counts, and binary subnet breakdown.

Input 10.0.5.23 /16
IP class A
Network bits 16
Host bits 16
Network address 10.0.0.0
Broadcast address 10.0.255.255
Subnet mask 255.255.0.0
Wildcard mask 0.0.255.255
Total addresses 65,536
Usable hosts 65,534
First usable host 10.0.0.1
Last usable host 10.0.255.254

What this means

The IPv4 address 10.0.5.23 belongs to the 10.0.0.0/16 network, and the subnet broadcast boundary is 10.0.255.255.

This subnet provides 65,536 total addresses and 65,534 usable host addresses, with a host range from 10.0.0.1 to 10.0.255.254.

The subnet mask is 255.255.0.0, the wildcard mask is 0.0.255.255, and the address falls into Class A.

Common presets

192.168.1.10 /24 10.0.5.23 /16 172.16.10.200 /20 192.168.100.14 /27 203.0.113.9 /30 198.51.100.10 /31 203.0.113.44 /32

Binary breakdown

Inspect the binary representation of the IP, subnet mask, network, and broadcast values.

IP address

00001010.00000000.00000101.00010111

Subnet mask

11111111.11111111.00000000.00000000

Network address

00001010.00000000.00000000.00000000

Broadcast address

00001010.00000000.11111111.11111111

CIDR quick notes

Useful reminders for subnetting and host calculations.

/24 means 24 network bits and 8 host bits.

Subnet mask shows the network boundary, while wildcard mask is its inverse.

/31 is commonly used for point-to-point links, while /32 represents a single-host route.

CIDR quick reference

Common IPv4 subnet sizes for fast comparison without recalculating each time.

Prefix Subnet mask Total addresses Usable hosts
/16 255.255.0.0 65,536 65,534
/17 255.255.128.0 32,768 32,766
/18 255.255.192.0 16,384 16,382
/19 255.255.224.0 8,192 8,190
/20 255.255.240.0 4,096 4,094
/21 255.255.248.0 2,048 2,046
/22 255.255.252.0 1,024 1,022
/23 255.255.254.0 512 510
/24 255.255.255.0 256 254
/25 255.255.255.128 128 126
/26 255.255.255.192 64 62
/27 255.255.255.224 32 30
/28 255.255.255.240 16 14
/29 255.255.255.248 8 6
/30 255.255.255.252 4 2
/31 255.255.255.254 2 2
/32 255.255.255.255 1 1