Subnet Calculator
Reserved for future use
240.0.0.0/4RFC 1112 held this back as class E. Most stacks refuse to use it, and no registry allocates from it.
Not announced in BGP, so there is no operator or routing to show.
240.0.0.0
240.0.0.0
247.255.255.255
/5
240.0.0.1
247.255.255.254
Network Information
134,217,728
134,217,726
240.0.0.1 – 247.255.255.254
Subnet Cheat Sheet
| CIDR | Subnet Mask | Wildcard Mask | Total IPs | Usable Hosts | Network Bits | Host Bits |
|---|---|---|---|---|---|---|
| /32 | 255.255.255.255 | 0.0.0.0 | 1 | 1 | 32 | 0 |
| /31 | 255.255.255.254 | 0.0.0.1 | 2 | 2 | 31 | 1 |
| /30 | 255.255.255.252 | 0.0.0.3 | 4 | 2 | 30 | 2 |
| /29 | 255.255.255.248 | 0.0.0.7 | 8 | 6 | 29 | 3 |
| /28 | 255.255.255.240 | 0.0.0.15 | 16 | 14 | 28 | 4 |
| /27 | 255.255.255.224 | 0.0.0.31 | 32 | 30 | 27 | 5 |
| /26 | 255.255.255.192 | 0.0.0.63 | 64 | 62 | 26 | 6 |
| /25 | 255.255.255.128 | 0.0.0.127 | 128 | 126 | 25 | 7 |
| /24 | 255.255.255.0 | 0.0.0.255 | 256 | 254 | 24 | 8 |
| /23 | 255.255.254.0 | 0.0.1.255 | 512 | 510 | 23 | 9 |
| /22 | 255.255.252.0 | 0.0.3.255 | 1,024 | 1,022 | 22 | 10 |
| /21 | 255.255.248.0 | 0.0.7.255 | 2,048 | 2,046 | 21 | 11 |
| /20 | 255.255.240.0 | 0.0.15.255 | 4,096 | 4,094 | 20 | 12 |
| /19 | 255.255.224.0 | 0.0.31.255 | 8,192 | 8,190 | 19 | 13 |
| /18 | 255.255.192.0 | 0.0.63.255 | 16,384 | 16,382 | 18 | 14 |
| /17 | 255.255.128.0 | 0.0.127.255 | 32,768 | 32,766 | 17 | 15 |
| /16 | 255.255.0.0 | 0.0.255.255 | 65,536 | 65,534 | 16 | 16 |
| /15 | 255.254.0.0 | 0.1.255.255 | 131,072 | 131,070 | 15 | 17 |
| /14 | 255.252.0.0 | 0.3.255.255 | 262,144 | 262,142 | 14 | 18 |
| /13 | 255.248.0.0 | 0.7.255.255 | 524,288 | 524,286 | 13 | 19 |
| /12 | 255.240.0.0 | 0.15.255.255 | 1,048,576 | 1,048,574 | 12 | 20 |
| /11 | 255.224.0.0 | 0.31.255.255 | 2,097,152 | 2,097,150 | 11 | 21 |
| /10 | 255.192.0.0 | 0.63.255.255 | 4,194,304 | 4,194,302 | 10 | 22 |
| /9 | 255.128.0.0 | 0.127.255.255 | 8,388,608 | 8,388,606 | 9 | 23 |
| /8 | 255.0.0.0 | 0.255.255.255 | 16,777,216 | 16,777,214 | 8 | 24 |
| /7 | 254.0.0.0 | 1.255.255.255 | 33,554,432 | 33,554,430 | 7 | 25 |
| /6 | 252.0.0.0 | 3.255.255.255 | 67,108,864 | 67,108,862 | 6 | 26 |
| /5 | 248.0.0.0 | 7.255.255.255 | 134,217,728 | 134,217,726 | 5 | 27 |
| /4 | 240.0.0.0 | 15.255.255.255 | 268,435,456 | 268,435,454 | 4 | 28 |
| /3 | 224.0.0.0 | 31.255.255.255 | 536,870,912 | 536,870,910 | 3 | 29 |
| /2 | 192.0.0.0 | 63.255.255.255 | 1,073,741,824 | 1,073,741,822 | 2 | 30 |
| /1 | 128.0.0.0 | 127.255.255.255 | 2,147,483,648 | 2,147,483,646 | 1 | 31 |
| /0 | 0.0.0.0 | 255.255.255.255 | 4,294,967,296 | 4,294,967,294 | 0 | 32 |
Quick Reference
How to Use
Enter an IP address and CIDR prefix above to calculate subnet details including network address, broadcast address, subnet mask, and usable host range.
CIDR Notation
CIDR (Classless Inter-Domain Routing) replaced traditional classful networking. The prefix length (e.g., /24) specifies how many bits identify the network, with the remaining bits identifying hosts.
Common Subnet Sizes
/24 (254 hosts) is the most common LAN size. /16 (65,534 hosts) suits large campuses. /30 (2 hosts) is used for point-to-point links. /32 represents a single host.
Mobile networks rarely hand a phone a public address of its own: most carriers put subscribers behind CGNAT in 100.64.0.0/10, which is why a phone’s IP so seldom matches the subnet you expect.