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IP Subnet Calculator (CIDR)
Enter an IPv4 address with a prefix like /24 or a mask like 255.255.255.0 to see the network, broadcast, host range and more — then split it into smaller subnets.
Subnet details
| Network address | 192.168.1.0 | |
|---|---|---|
| CIDR notation | 192.168.1.0/24 | |
| Subnet mask | 255.255.255.0 | |
| Wildcard mask | 0.0.0.255 | |
| Broadcast address | 192.168.1.255 | |
| First usable host | 192.168.1.1 | |
| Last usable host | 192.168.1.254 | |
| Usable hosts | 254 | |
| Total addresses | 256 | |
| Mask in binary | 11111111.11111111.11111111.00000000 | |
| Address type | Private (RFC 1918) |
Split into smaller subnets
When should you use the Subnet Calculator?
- Planning VPC and subnet ranges in AWS, Azure or GCP
- Working out the usable host range for a network or firewall rule
- Splitting a /16 or /24 into equal smaller subnets
How to use the Subnet Calculator
- 1
Enter an address
Use CIDR (192.168.1.10/24) or an address and mask (192.168.1.10 255.255.255.0).
- 2
Read the details
Network, broadcast, first and last host, masks and host counts appear instantly.
- 3
Change the prefix
Pick another prefix from the list to compare sizes.
- 4
Split it
Choose a longer prefix to list every smaller subnet inside.
Examples
192.168.1.10/24
Input
192.168.1.10/24
Result
Network 192.168.1.0 Broadcast 192.168.1.255 Host range 192.168.1.1 – 192.168.1.254 Usable hosts 254 Mask 255.255.255.0
Common errors and how to fix them
Isn't a valid subnet mask- A mask's 1 bits must be continuous from the left — 255.255.255.0 is valid, 255.0.255.0 isn't.
Cloud providers say fewer hosts are available- AWS and Azure reserve extra addresses in each subnet (AWS keeps 5), so usable hosts are a little lower there.
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Subnet Calculator FAQ
The first 24 bits are the network part, leaving 8 bits for hosts: 256 addresses, 254 usable. It's the same as the mask 255.255.255.0.
The first address identifies the network and the last is the broadcast address, so neither can be given to a device. /31 and /32 are exceptions.
The inverse of the subnet mask (0.0.0.255 for /24), used in Cisco ACLs and OSPF.
/16 has 65,534 usable hosts, /24 has 254 and /28 has 14. The formula is 2^(32 − prefix) − 2.
This calculator handles IPv4. For IPv6 address formats, use the IP Address Converter.
No. Everything runs in your browser, so your data never leaves your device.