IP addressing made simple
Subnet Calculator
Calculate network details for any IPv4 or IPv6 address and CIDR prefix. Get the network address, subnet mask, usable hosts, and broadcast instantly.
- Instant results
- Visual representation
- Learn with examples
- Free to use
Results
Network details for 0.0.0.0/31
Network Address
0.0.0.0
Broadcast Address
0.0.0.1
Subnet Mask
255.255.255.254
Total Addresses
2
Usable Hosts
2
First Host
0.0.0.0
Last Host
0.0.0.1
Wildcard Mask
0.0.0.1
Binary Representation
Visual Representation
RFC 3021 uses both addresses as hosts. The network and broadcast labels still mark the two ends.
- IP Range CalculatorRead the inclusive address range of a subnet, and the usable hosts inside it.
- Subnet SplitterDivide a network into smaller, equal, non-overlapping subnets.
- Subnet MergerFind the smallest subnet that contains multiple networks.
- IP Address ConverterConvert between decimal, binary, hexadecimal, and CIDR.
Common CIDR Prefixes
Quick reference table of common IPv4 CIDR prefixes.
| CIDR | Subnet Mask | Total Addresses | Usable Hosts |
|---|---|---|---|
| /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 |
Learn Subnetting
Step-by-step guides to help you understand IP addressing.
- 1What is a subnet?Learn the basics of IP addressing and subnets.
- 2Understanding CIDR notationHow CIDR works and how to read it.
- 3How to calculate subnetsA worked example, from the address to the usable range.
- 4VLSM (Variable Length Subnet Masking)Advanced subnetting for efficient IP allocation.
Frequently Asked Questions
Common questions about subnetting and IP addressing.
A subnet is a contiguous block of IP addresses that share the same network prefix. The prefix length says how many leading bits are the network. The remaining bits distinguish hosts inside that block.
CIDR notation writes an address and a prefix length, as in 192.168.1.0/24. The /24 means the first 24 bits are the network. That prefix is the subnet mask 255.255.255.0.
For a conventional IPv4 prefix from /0 through /30, usable hosts are 2 to the power of the host bits, minus 2. The network address and the broadcast are the two addresses that are not hosts. A /24 has 8 host bits, so 256 total addresses and 254 usable hosts.
A /30 has 4 addresses and 2 usable hosts under the usual network-and-broadcast rule. A /31 also has 2 addresses, and RFC 3021 uses both of them as hosts on a point-to-point link. Subtracting 2 from a /31 would hide those hosts.
Host counts for /31 follow RFC 3021. Prefix rules follow RFC 4632. The method is written up on the methodology page.
