Enter an IPv4 address and CIDR prefix to instantly get the network address, broadcast address, subnet mask, wildcard mask, usable host range, and IP address class.
Enter an IP address and CIDR prefix to see the subnet breakdown
Subnetting is the process of splitting a larger IPv4 network into smaller, self-contained segments — and doing the binary math by hand is tedious and error-prone. This IP subnet calculator takes any IPv4 address and CIDR prefix length (from /8 down to /30) and instantly returns the network address, broadcast address, subnet mask, wildcard mask, first and last usable host, total address count, usable host count, and the legacy IP address class, all computed with real bitwise operations rather than a lookup table.
It validates your IPv4 address, converts it to a 32-bit integer, derives the subnet mask from your chosen CIDR prefix, and runs bitwise AND/OR/NOT operations to compute the network address, broadcast address, wildcard mask, and usable host range.
Network administrators planning VLANs, cloud engineers sizing VPC CIDR blocks, students studying for networking certifications (CCNA, Network+), and anyone troubleshooting a "can't reach this device" issue caused by a subnet mask mismatch all need this exact bitwise subnetting math.
Correct subnetting prevents two very common and disruptive networking mistakes: assigning overlapping address ranges to different network segments, and under- or over-sizing a subnet so it either runs out of host addresses too soon or wastes a large block of address space that could serve other segments. Whether you're designing VLANs for an office, carving out address space for a cloud VPC, or just studying for a networking certification, seeing the exact network boundaries, broadcast address, and usable host range for a given prefix removes the guesswork from IP address planning.
The bitwise math this calculator uses, the same a router's firmware performs
The /31 exception (RFC 3021) treats both addresses in a 2-address block as usable, since there's no room for a separate network/broadcast address — the standard choice for point-to-point router links. A /32 identifies a single host with no range at all.
CIDR notation like /24 tells you how many of the 32 bits in an IPv4 address are the fixed "network" portion. The remaining bits are the "host" portion.
The network address (all host bits 0) identifies the subnet itself and the broadcast address (all host bits 1) reaches every device on it. Neither can be assigned to a host.
Before CIDR, IPv4 space was divided into classes: A (1–126, /8), B (128–191, /16), C (192–223, /24), D (multicast), E (experimental). Legacy today, but still referenced.
From entering an address to reading the full subnet breakdown
Type any IPv4 address in dotted-decimal form, such as 192.168.1.0 — you don't need to know the exact network address in advance.
Select a prefix from /8 through /30 from the dropdown, which also previews the resulting subnet mask and usable host count.
The calculator validates the address, converts it to a 32-bit integer, and runs the bitwise AND/OR/NOT operations needed to derive every subnet field.
Read the network address, broadcast address, subnet mask, wildcard mask, first/last usable host, total addresses, usable hosts, IP class, and the binary view.
Download a plain-text summary with Export Result, or click Reset to return to the default address and prefix and calculate another subnet.
Using the calculator's own default scenario — 192.168.1.0/24
Suppose you enter the address 192.168.1.0 with a /24 CIDR prefix.
Explanation: A /24 leaves 8 host bits (2⁸ = 256 total addresses), and after reserving the network and broadcast addresses, 254 remain usable — the classic "Class C-sized" subnet, commonly used for small office LANs and home networks even though CIDR has replaced formal class-based addressing.
What each result field means when configuring a network
| Field | What It Means | How to Use It |
|---|---|---|
| Network Address | Identifies the subnet itself | Use as the subnet's route entry, not a host address |
| Broadcast Address | Reaches every device on the subnet | Never assign to a device |
| First/Last Usable Host | The assignable address range | Configure devices within this range |
| Usable Hosts | How many devices the subnet can hold | Compare against your expected device count plus growth |
If usable hosts is smaller than your device count: choose a shorter prefix (fewer bits, e.g. /23 instead of /24) to get more host addresses.
If usable hosts is far larger than your device count: consider a longer prefix (more bits, e.g. /27) to avoid wasting address space that could serve another segment.
This tool's bitwise math is exact, but it can't detect overlapping ranges across your broader network — cross-check against your IPAM records before deploying.
This calculator performs exact bitwise subnetting math but does not validate reachability, routing, or whether an address is actually available on your network.
Where exact subnet math genuinely helps
Split a larger network into per-department or per-floor VLANs with the right host count each.
Size an AWS, Azure, or GCP VPC CIDR block before subdividing it per availability zone.
Understand your router's default subnet and plan static IP assignments within it.
Use exact network/broadcast boundaries when writing firewall or ACL rules by subnet.
Set a DHCP pool's start/end addresses correctly within the usable host range.
Use a /31 subnet for router-to-router WAN links per RFC 3021.
Practice CIDR and subnetting problems for CCNA, Network+, or similar exams.
Diagnose a mismatched subnet mask causing "can't reach this device" problems.
Plan subnets for server racks, management networks, and storage VLANs.
Verify a candidate CIDR block doesn't overlap before setting up VPC peering or a VPN.
Use it in a networking course to make binary AND/OR/NOT operations concrete.
Recompute subnet boundaries whenever a network topology or IP plan changes.
What this IP subnet calculator does well, and where it can't replace network validation
Subnet mask, total addresses, and usable hosts by prefix
| Prefix | 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 |
Summary: This IP subnet calculator gives you an instant, free, exact bitwise breakdown of any IPv4 address and CIDR prefix — network address, broadcast address, mask, wildcard, and usable host range — removing the guesswork from subnetting. Pair it with the DNS Propagation Estimator and Bandwidth Calculator for a fuller networking toolkit.
Common questions about IP subnet calculator results
Official standards documentation to complement this calculator
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