Live tool

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
Open calculator

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 203.0.113.9 /30
IP class C
Network bits 30
Host bits 2
Network address 203.0.113.8
Broadcast address 203.0.113.11
Subnet mask 255.255.255.252
Wildcard mask 0.0.0.3
Total addresses 4
Usable hosts 2
First usable host 203.0.113.9
Last usable host 203.0.113.10

What this means

The IPv4 address 203.0.113.9 belongs to the 203.0.113.8/30 network, and the subnet broadcast boundary is 203.0.113.11.

This subnet provides 4 total addresses and 2 usable host addresses, with a host range from 203.0.113.9 to 203.0.113.10.

The subnet mask is 255.255.255.252, the wildcard mask is 0.0.0.3, and the address falls into Class C.

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

11001011.00000000.01110001.00001001

Subnet mask

11111111.11111111.11111111.11111100

Network address

11001011.00000000.01110001.00001000

Broadcast address

11001011.00000000.01110001.00001011

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