IP Subnet Calculator
Netmask, network, broadcast, and usable hosts from an IP and CIDR.
Calculate the netmask, network address, broadcast address, and usable host range for an IPv4 address and CIDR prefix. Free and instant, in your browser.
How to read the results
For 192.168.1.10/24:
- Subnet mask: 255.255.255.0
- Network address: 192.168.1.0 — identifies the subnet itself
- Broadcast address: 192.168.1.255 — reaches every device on the subnet
- Usable hosts: 192.168.1.1 to 192.168.1.254 — 254 addresses for devices
A smaller subnet works the same way. For 192.168.10.77/26, the network is 192.168.10.64 and the broadcast is 192.168.10.127, leaving 62 usable addresses.
CIDR cheat sheet
| Prefix | Subnet mask | Total addresses | Usable hosts |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,216 | 16,777,214 |
| /16 | 255.255.0.0 | 65,536 | 65,534 |
| /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 |
Each step up in the prefix halves the subnet. The total number of addresses is 2 to the power of (32 − prefix).
Private IP ranges
These ranges are reserved for home and office networks and aren't reachable directly from the internet:
- 10.0.0.0/8 — large company networks
- 172.16.0.0/12 — medium networks, and many cloud and Docker setups
- 192.168.0.0/16 — almost every home router
Your home router typically uses a /24 such as 192.168.0.0/24 or 192.168.1.0/24, which allows up to 254 devices.
Frequently asked questions
What does the CIDR prefix (the /24 part) mean?
It's the number of bits used for the network portion of the address — a /24 means the first 24 bits identify the network, leaving 8 bits (256 addresses) for hosts.
Why is the usable host count 2 less than the total?
The first address in a subnet is reserved as the network address, and the last is reserved as the broadcast address — neither can be assigned to a device.
How do I choose a subnet size?
Count the devices you need now, add room for growth, and pick the smallest subnet with enough usable hosts. For 40 devices, a /26 (62 usable) is a good fit; a /27 (30 usable) would be too small.
Does this work for IPv6?
No — this calculator is for IPv4 addresses. IPv6 uses 128-bit addresses and different conventions, with /64 the standard size for a single network.