HomeCIDR Chart
IPv4 CIDR Chart.
Complete reference for all IPv4 prefix lengths from /1 to /32. Click any prefix to open it in the calculator.
Most common
Special purpose
| CIDR | Subnet Mask | Wildcard Mask | Total Addresses | Usable Hosts | Block Size | Notes | |
|---|---|---|---|---|---|---|---|
| /0 | 0.0.0.0 | 255.255.255.255 | 4,294,967,296 | 4,294,967,294 | 4,294,967,296 | Entire IPv4 space | Calculate → |
| /1 | 128.0.0.0 | 127.255.255.255 | 2,147,483,648 | 2,147,483,646 | 2,147,483,648 | Calculate → | |
| /2 | 192.0.0.0 | 63.255.255.255 | 1,073,741,824 | 1,073,741,822 | 1,073,741,824 | Calculate → | |
| /3 | 224.0.0.0 | 31.255.255.255 | 536,870,912 | 536,870,910 | 536,870,912 | Calculate → | |
| /4 | 240.0.0.0 | 15.255.255.255 | 268,435,456 | 268,435,454 | 268,435,456 | Calculate → | |
| /5 | 248.0.0.0 | 7.255.255.255 | 134,217,728 | 134,217,726 | 134,217,728 | Calculate → | |
| /6 | 252.0.0.0 | 3.255.255.255 | 67,108,864 | 67,108,862 | 67,108,864 | Calculate → | |
| /7 | 254.0.0.0 | 1.255.255.255 | 33,554,432 | 33,554,430 | 33,554,432 | Calculate → | |
| /8 | 255.0.0.0 | 0.255.255.255 | 16,777,216 | 16,777,214 | 16,777,216 | Class A | Calculate → |
| /9 | 255.128.0.0 | 0.127.255.255 | 8,388,608 | 8,388,606 | 8,388,608 | Calculate → | |
| /10 | 255.192.0.0 | 0.63.255.255 | 4,194,304 | 4,194,302 | 4,194,304 | Calculate → | |
| /11 | 255.224.0.0 | 0.31.255.255 | 2,097,152 | 2,097,150 | 2,097,152 | Calculate → | |
| /12 | 255.240.0.0 | 0.15.255.255 | 1,048,576 | 1,048,574 | 1,048,576 | Calculate → | |
| /13 | 255.248.0.0 | 0.7.255.255 | 524,288 | 524,286 | 524,288 | Calculate → | |
| /14 | 255.252.0.0 | 0.3.255.255 | 262,144 | 262,142 | 262,144 | Calculate → | |
| /15 | 255.254.0.0 | 0.1.255.255 | 131,072 | 131,070 | 131,072 | Calculate → | |
| /16 | 255.255.0.0 | 0.0.255.255 | 65,536 | 65,534 | 65,536 | Class B | Calculate → |
| /17 | 255.255.128.0 | 0.0.127.255 | 32,768 | 32,766 | 32,768 | Calculate → | |
| /18 | 255.255.192.0 | 0.0.63.255 | 16,384 | 16,382 | 16,384 | Calculate → | |
| /19 | 255.255.224.0 | 0.0.31.255 | 8,192 | 8,190 | 8,192 | Calculate → | |
| /20 | 255.255.240.0 | 0.0.15.255 | 4,096 | 4,094 | 4,096 | Calculate → | |
| /21 | 255.255.248.0 | 0.0.7.255 | 2,048 | 2,046 | 2,048 | Calculate → | |
| /22 | 255.255.252.0 | 0.0.3.255 | 1,024 | 1,022 | 1,024 | Calculate → | |
| /23 | 255.255.254.0 | 0.0.1.255 | 512 | 510 | 512 | Calculate → | |
| /24 | 255.255.255.0 | 0.0.0.255 | 256 | 254 | 256 | Class C — most common | Calculate → |
| /25 | 255.255.255.128 | 0.0.0.127 | 128 | 126 | 128 | Half a /24 | Calculate → |
| /26 | 255.255.255.192 | 0.0.0.63 | 64 | 62 | 64 | Quarter /24 | Calculate → |
| /27 | 255.255.255.224 | 0.0.0.31 | 32 | 30 | 32 | Calculate → | |
| /28 | 255.255.255.240 | 0.0.0.15 | 16 | 14 | 16 | Common in cloud VPCs | Calculate → |
| /29 | 255.255.255.248 | 0.0.0.7 | 8 | 6 | 8 | Calculate → | |
| /30 | 255.255.255.252 | 0.0.0.3 | 4 | 2 | 4 | Point-to-point links | Calculate → |
| /31 | 255.255.255.254 | 0.0.0.1 | 2 | 2 | 2 | RFC 3021 — P2P no broadcast | Calculate → |
| /32 | 255.255.255.255 | 0.0.0.0 | 1 | 1 | 1 | Single host route | Calculate → |
How to read this chart
CIDR — The prefix length (e.g. /24). The number of 1-bits in the subnet mask.
Subnet Mask — The dotted-decimal representation of the mask (e.g. 255.255.255.0).
Wildcard Mask — Bitwise inverse of the subnet mask. Used in Cisco ACLs and OSPF.
Total Addresses — All addresses in the subnet = 2^(32-prefix).
Usable Hosts — Total minus network and broadcast addresses.
Block Size — The number of addresses between consecutive subnets at this prefix length.
Private IP Ranges
These ranges are reserved for private use (RFC 1918) and are never routed on the public internet:
10.0.0.0/8— 16,777,214 hosts172.16.0.0/12— 1,048,574 hosts192.168.0.0/16— 65,534 hosts
Special ranges:
127.0.0.0/8— Loopback169.254.0.0/16— Link-local (APIPA)224.0.0.0/4— Multicast