Subnet calculator
IP + CIDR → network, broadcast, host range and masks.
- Instant
- Free
- Private (processed locally)
- No sign-up
Know everything about a subnet from an IP and a /prefix
Splitting a network into subnets is everyday system administration. From an IPv4 address and its CIDR prefix, this tool computes in bits — like a router does — the network address, broadcast, host range, mask and wildcard.
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Enter IP/CIDR
For example 192.168.1.10/24.
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Read the split
Network, broadcast, first and last host, full range.
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Grab the masks
Subnet mask and inverse wildcard mask.
Example: 192.168.1.10/24
| Item | Value |
|---|---|
| Network address | 192.168.1.0/24 |
| Broadcast | 192.168.1.255 |
| Host range | 192.168.1.1 – 192.168.1.254 |
| Usable hosts | 254 |
| Mask | 255.255.255.0 |
| Wildcard | 0.0.0.255 |
IPv4 calculation with bitwise operations, no network connection. For a /26, you would get 4 subnets of 62 hosts each — change the prefix to see the split recompute.
Frequently asked questions
What is CIDR notation (/24)?
The number after the “/” says how many bits, from the left, identify the network. /24 = 24 network bits, leaving 8 bits for hosts (2⁸ = 256 addresses). The bigger the number, the smaller the subnet.
Why 254 usable hosts and not 256 on a /24?
Two addresses are reserved in each subnet: the first is the network address (identifies the network), the last is the broadcast address (send to all). That leaves 256 − 2 = 254 addresses assignable to machines.
What is the wildcard mask for?
It is the bitwise inverse of the subnet mask (0.0.0.255 for a /24). It is mostly used in Cisco access control lists (ACLs), where you think in “bits to ignore” rather than “bits to check”.
What happens with /31 and /32?
A /32 denotes a single address (one specific host). A /31 (RFC 3021) is a special case for point-to-point links: its 2 addresses are both usable, with no network or broadcast. The tool then shows 0 “classic” hosts but the range is still valid.