Subnet Calculator
Calculate the network address, broadcast address, subnet mask, and usable host range for any IPv4 address and CIDR prefix.
- Free to use
- No registration required
- Works on all devices
- Last updated
- 12-09-2026
Your result
192.168.1.0
Network address
AI explanation
Formula
Network = IP AND Mask; Broadcast = Network OR (NOT Mask); usable range excludes network/broadcast except for /31 and /32Worked example
192.168.1.10 / 24
| Field | Value |
|---|---|
| IPv4 address | 192.168.1.10 |
| CIDR prefix length | 24 |
| Network address | 192.168.1.0 |
| Broadcast address | 192.168.1.255 |
| Subnet mask | 255.255.255.0 |
| First usable host | 192.168.1.1 |
| Last usable host | 192.168.1.254 |
| Usable host count | 254 |
Assumptions
- IPv4 only (no IPv6 support in this calculator).
- /31 networks follow RFC 3021 (2 usable point-to-point addresses, no separate broadcast); /32 is treated as a single host route.
Frequently asked questions
What is CIDR notation?
Classless Inter-Domain Routing notation expresses a subnet mask as a prefix length (e.g. /24) — the number of leading 1-bits in the mask — rather than as a full dotted-decimal mask.
What is the difference between the network address and the first usable host?
The network address (e.g. 192.168.1.0) identifies the subnet itself and cannot be assigned to a device. The first usable host is one address above it.
Why does a /31 subnet not have a separate broadcast address?
RFC 3021 defines /31 subnets specifically for point-to-point links, allowing both addresses in the 2-address block to be used as hosts, since a broadcast address isn't needed on a link with only two endpoints.
How many usable hosts does a /24 network have?
254 — a /24 has 256 total addresses, minus 1 for the network address and 1 for the broadcast address.
What does the number after the slash mean in CIDR notation?
It's the prefix length — the number of leading bits (out of 32 for IPv4) that identify the network portion of the address, with the remaining bits available for host addresses.
How do I convert a CIDR prefix to a subnet mask?
Set the first n bits to 1 and the rest to 0, then group into 4 octets — e.g. /28 gives 11111111.11111111.11111111.11110000, or 255.255.255.240 in dotted-decimal.
Why use CIDR instead of separate subnet masks?
CIDR notation is more compact and enables "supernetting" — combining multiple smaller networks into a single larger routing entry, reducing the size of internet routing tables.