CIDR Notation	Subnet Mask	# of Subnets (if borrowing)	# of Hosts per Subnet	Block Size
/24	255.255.255.0	1	254	1
/25	255.255.255.128	2	126	128
/26	255.255.255.192	4	62	64
/27	255.255.255.224	8	30	32
/28	255.255.255.240	16	14	16
/29	255.255.255.248	32	6	8
/30	255.255.255.252	64	2	4
/31*	255.255.255.254	128	0 or 2 (special case)	2
/32	255.255.255.255	Host only	1 (only the device)	1

How to Quickly Calculate Subnet Ranges:

1. Find the Block Size.

2. Start at 0 and add the block size each time.

3. Example for /26 (block size 64):

   • Subnets: 0, 64, 128, 192

   • Ranges:

     • 192.168.1.0 – 192.168.1.63

     • 192.168.1.64 – 192.168.1.127

     • 192.168.1.128 – 192.168.1.191

     • 192.168.1.192 – 192.168.1.255

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Given: IP = 192.168.10.0/27

• Subnet Mask: 255.255.255.224

• Block Size: 32

• Ranges:

  • 192.168.10.0 – 192.168.10.31

  • 192.168.10.32 – 192.168.10.63

  • 192.168.10.64 – 192.168.10.95

  • and so on.

Each range gives you 30 usable hosts.

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Would you also like me to make a one-page visual chart (like a clean graphic) you can download too? 🎯
It would be even easier to print and stick on your wall or binder!