IP Subnet Calculator (CIDR)
Find the network address, broadcast, netmask, host range, and host count from an IPv4 address and CIDR prefix. Instant and fully client-side.
Runs in your browser — nothing uploaded
CIDR notation192.168.1.0/24
Subnet mask255.255.255.0
Wildcard mask0.0.0.255
Network address192.168.1.0
Broadcast address192.168.1.255
First usable host192.168.1.1
Last usable host192.168.1.254
Total addresses256
Usable hosts254
Enter an IPv4 address and a CIDR prefix to get the full picture of its subnet: network address, broadcast address, subnet mask, wildcard mask, the first and last usable host, and the total and usable host counts. Handy for planning networks, configuring routers and firewalls, and studying for networking certifications.
Private by design — your data never leaves your device
How to use it
No account, no upload — it all happens on your device.
1
Type an IPv4 address, for example 192.168.1.10.
2
Pick the CIDR prefix — the dropdown shows the matching subnet mask for each one.
3
Read the network and broadcast addresses, usable host range, and host count.
4
Click the copy icon next to any address to copy it.
Common prefixes at a glance
How the prefix maps to a mask and host count.
| CIDR | Subnet mask | Usable hosts |
|---|---|---|
| /30 | 255.255.255.252 | 2 |
| /29 | 255.255.255.248 | 6 |
| /24 | 255.255.255.0 | 254 |
| /16 | 255.255.0.0 | 65,534 |
| /8 | 255.0.0.0 | 16,777,214 |
What each result means
- Network address. The first address in the block — it names the subnet and is never assigned to a host.
- Broadcast address. The last address — traffic sent here reaches every host on the subnet. Also unassignable.
- Subnet mask & wildcard. The mask marks the network bits; the wildcard (its inverse) is what ACLs and OSPF use to match host bits.
- Usable host range. Every address between the network and broadcast — these are the IPs you can hand to devices.
Frequently asked
What does the CIDR prefix (the /24) mean?
The prefix is the number of leading bits that identify the network. A /24 means the first 24 bits are the network and the last 8 bits are hosts, giving a 255.255.255.0 mask and 254 usable addresses. A smaller prefix like /16 covers far more hosts; a larger one like /30 covers only a handful.
Why are there two fewer usable hosts than total addresses?
In each subnet, the first address is reserved as the network identifier and the last is the broadcast address, so neither can be assigned to a device. A /24 therefore has 256 total addresses but 254 usable hosts. (/31 and /32 are special cases used for point-to-point and single-host links.)
Is the IP address I enter sent anywhere?
No. Every value is computed from bit math in your browser. The address you type is never uploaded, logged, or shared.