🧮 CIDR & Subnet Calculator
Calculate any IPv4 or IPv6 subnet in seconds: network address, broadcast or last address, wildcard mask and usable host range. Built for students and network admins planning LANs or BDIX 10.x address space.
Enter an address and prefix (or a full block like 10.16.0.0/16). The calculator shows the network address, broadcast, wildcard and the first/last usable IPs: everything you need to plan or audit a subnet.
| Network address | - |
|---|---|
| Broadcast / last address | - |
| Subnet mask | - |
| Wildcard mask | - |
| Usable range | - |
| Total addresses | - |
| Usable hosts | - |
Common IPv4 Subnet Masks
| Prefix | Subnet mask | Usable hosts | Typical use |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 | Large private networks (10.0.0.0/8) |
| /16 | 255.255.0.0 | 65,534 | ISP / campus LANs |
| /24 | 255.255.255.0 | 254 | Home & office LANs |
| /25 | 255.255.255.128 | 126 | Small subnets |
| /30 | 255.255.255.252 | 2 | Point-to-point links |
| /32 | 255.255.255.255 | 1 | A single host |
When to Use a Subnet Calculator
- Planning a home or office network and choosing a suitable prefix.
- Splitting a larger block into smaller subnets for different departments or VLANs.
- Working out whether two IPs are on the same subnet (and so can talk directly).
- Understanding the private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16: used inside BDIX and ISP networks.
- Studying for networking exams and certifying your subnet math.
FAQ (Frequently Asked Questions)
What Is CIDR Notation?
CIDR (Classless Inter-Domain Routing) notation is a compact way to write a network: an address followed by a slash and the prefix length, such as 192.168.1.0/24. The prefix length is the number of leading bits that identify the network.
What Is a Subnet Mask?
A subnet mask is the same information as the prefix length, written as four octets for IPv4 (for example /24 = 255.255.255.0). Devices use it to decide which addresses are local and which must be routed.
What Is the Difference Between Network and Broadcast Address?
The network address is the first address in a block and identifies the network itself. The broadcast address is the last address, used to send a message to every host on the network at once. Neither can be assigned to a device.
How Many Usable Addresses Are in a /24?
A /24 has 256 total addresses, of which 254 are usable for hosts (the network and broadcast addresses are reserved). In general a /n IPv4 block has 2^(32-n) total addresses and 2^(32-n) - 2 usable ones.
Why Does the Calculator Show IPv6 Results As a Power of Two?
IPv6 blocks are huge. A /64 has 2^64 addresses: about 18.4 quintillion: which is unwieldy to print in full. We show the power-of-two form and the exact decimal when it is small enough to be useful.
Is 10.0.0.0/8 a BDIX Address?
The 10.0.0.0/8 range is the private range used heavily inside BDIX and Bangladeshi ISP networks. It is not reachable from the public internet: only from within an ISP’s own network or via BDIX peering.