Graph
Calculator
Example Data Table
| IP | Class | Type | Default Mask | Network (default) | Broadcast (default) | Usable Hosts (default) |
|---|---|---|---|---|---|---|
| 10.0.0.25 | A | Private | 255.0.0.0 | 10.0.0.0 | 10.255.255.255 | 16777214 |
| 172.16.8.10 | B | Private | 255.255.0.0 | 172.16.0.0 | 172.16.255.255 | 65534 |
| 192.168.1.100 | C | Private | 255.255.255.0 | 192.168.1.0 | 192.168.1.255 | 254 |
| 8.8.8.8 | A | Public | 255.0.0.0 | 8.0.0.0 | 8.255.255.255 | 16777214 |
| 224.0.0.5 | D | Multicast | N/A | N/A | N/A | N/A |
Examples use classful defaults for A, B, and C ranges.
Formula Used
- IP class: determined by the first octet range (A: 1–126, B: 128–191, C: 192–223, D: 224–239, E: 240–255).
- Subnet mask: from classful defaults (/8, /16, /24) or your CIDR/mask input.
- Network address: IP AND Mask.
- Broadcast address: Network OR (NOT Mask).
- Usable hosts: for /0–/30: 2^(32−prefix) − 2; for /31: 2; for /32: 1.
Tip: D and E ranges are not unicast host networks, so host math is shown as N/A.
How to Use This Calculator
- Choose Single IP or Batch list.
- Enter an IPv4 address, or paste multiple addresses.
- Select Classful default, CIDR prefix, or Subnet mask.
- Click Calculate to view results above the form.
- Use Download CSV or Download PDF to export.
Exports include class, type hints, and network fields when applicable.
Class boundaries by first octet
Class A spans 1–126 in the first octet, because 0 and 127 are reserved for special use. Class B spans 128–191, and Class C spans 192–223. Class D covers 224–239 for multicast groups, while Class E covers 240–255 for reserved experiments. The calculator reads the first octet, flags common special blocks, and assigns the matching class label.
Default masks and prefixes
In classful mode the default masks are 255.0.0.0 for Class A, 255.255.0.0 for Class B, and 255.255.255.0 for Class C. These correspond to /8, /16, and /24, meaning 8, 16, or 24 network bits. Historically this also implied 126 Class A networks, 16,384 Class B networks, and 2,097,152 Class C networks. When you choose CIDR or a custom mask, the prefix you supply overrides the default and drives all network math.
Network and broadcast computation
The network address is computed as IP AND Mask, and the broadcast address is Network OR (NOT Mask). The wildcard mask is NOT Mask. For example, /24 produces a wildcard of 0.0.0.255, /16 produces 0.0.255.255, and /30 produces 0.0.0.3. This calculator shows the dotted-decimal results and the binary form of the input IP.
Usable host totals
Total addresses equal 2^(32−prefix). For most subnets the usable host count is total minus 2, excluding the network and broadcast. That yields 16,777,216 total addresses for /8 and 16,777,214 usable hosts, 65,536 total for /16 and 65,534 usable hosts, and 256 total for /24 and 254 usable hosts. For /31 the tool reports 2 usable addresses (point-to-point), and for /32 it reports 1 (a single host route).
Private and shared ranges
Private space includes 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16, which should not be routed on the public internet. Shared carrier space is 100.64.0.0/10, often seen behind large NAT deployments. Documentation ranges include 192.0.2.0/24, 198.51.100.0/24, and 203.0.113.0/24, plus benchmarking space 198.18.0.0/15. The calculator tags these so you can spot lab, ISP, or public candidates quickly.
Special-purpose blocks
Loopback uses 127.0.0.0/8, link-local uses 169.254.0.0/16, and limited broadcast is 255.255.255.255. Addresses in Class D and Class E are not unicast hosts, so subnet fields show N/A. For batch lists, the graph summarizes how many entries fall into each class and helps you detect mixed data sets fast.
FAQs
1) What does an IP class tell me?
It indicates the traditional classful range based on the first octet. The class suggests a default mask (/8, /16, /24) and whether the address is unicast, multicast, or reserved.
2) Why does the calculator show N/A for some addresses?
Multicast (Class D) and reserved (Class E) addresses are not unicast host networks, so network, broadcast, and host-range fields do not apply in the usual way.
3) When should I use CIDR prefix mode?
Use CIDR when you know the exact prefix used on the network, such as /27 or /20. It reflects modern subnetting and produces accurate network and host ranges.
4) Why does /31 show two usable hosts?
On point-to-point links, /31 subnets can use both addresses without a network or broadcast host. The tool reports two usable addresses for that special case.
5) Does this tool validate custom subnet masks?
Yes. The mask must be a contiguous mask where 1-bits are followed only by 0-bits. Non-contiguous masks are rejected because they do not represent standard IPv4 subnetting.
6) Does it support IPv6 addresses?
No. This calculator focuses on IPv4 class ranges and subnet math. For IPv6, use prefix-based tools that handle hexadecimal notation and 128-bit addressing.