Subnet calculator
Calculate IPv4 subnets and CIDR ranges instantly. Free, private — nothing leaves your device.
192.168.1.0/24
Class C · Private (RFC 1918)
192.168.1.0192.168.1.255192.168.1.1192.168.1.254254256255.255.255.00.0.0.255Binary
- Address
11000000.10101000.00000001.00000000- Subnet mask
11111111.11111111.11111111.00000000- Network
11000000.10101000.00000001.00000000
Split into subnets
Everything you need to plan a subnet
Full subnet breakdown
Network, broadcast, first and last usable host, host count, mask, wildcard mask, and class.
CIDR and mask input
Type 192.168.1.0/24 or an address with a dotted mask. Both give the same answer.
Split into subnets
Divide a network into equal smaller subnets and see each range at a glance.
Binary view
See the address, mask, and network in binary, so the network and host bits are visible.
Private by design
Every calculation runs in your browser. Nothing you type is sent anywhere.
Edge cases handled
/31 point-to-point links, /32 hosts, and /0 are calculated correctly, and bad masks are caught.
Calculate a subnet in three steps
- 1
Enter an address and prefix
Type an IPv4 address with a CIDR prefix like 192.168.1.0/24, or with a subnet mask like 192.168.1.0 255.255.255.0.
- 2
Read the results
See the network address, broadcast address, first and last usable host, usable host count, subnet mask, wildcard mask, and the binary view.
- 3
Split into smaller subnets
Pick a longer prefix to divide the network into equal subnets, then copy any value you need.
Built for network admins, developers, and students
Subnetting splits an IP network into smaller blocks. Whether you are sizing a cloud VPC, writing a firewall rule, or studying for a networking exam, you need the network address, the host range, and the mask right.
Network and VPC planning
Size subnets for a cloud VPC, VLAN, or office network before you create them.
Firewall and routing rules
Find the exact network and wildcard mask for an ACL, route, or security group entry.
Studying for networking exams
Check your by-hand subnetting answers and watch the binary view to see why they work.
Troubleshooting
Confirm whether two addresses sit in the same subnet, or what range a device should be using.
Frequently asked questions
How do I calculate a subnet from a CIDR prefix?
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Enter the address and prefix, like 10.0.0.0/22. The calculator turns the prefix into a mask (here 255.255.252.0), applies it to the address to find the network address, and fills every host bit with 1s to find the broadcast address. Everything between the two is your host range.
Is this a CIDR calculator too?
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Yes. CIDR notation (the /24 after an address) is just another way to write a subnet mask, so the same page converts between the two. Enter 192.168.1.0/24 or 192.168.1.0 255.255.255.0 and you get the same result, including the prefix length and the dotted mask.
How many usable hosts does a /24 have?
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254. A /24 has 256 addresses in total, and the first (network address) and last (broadcast address) are reserved, leaving 254 for devices. In general, usable hosts = 2^(32 - prefix) - 2.
What happens with /31 and /32 networks?
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A /32 is a single host address, so it shows 1 usable address. A /31 has just 2 addresses and is used for point-to-point links (RFC 3021), so both count as usable and there is no separate broadcast reservation.
What is a wildcard mask?
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The inverse of the subnet mask: 0s where the mask has 1s and 1s where it has 0s. A /24 mask of 255.255.255.0 has the wildcard 0.0.0.255. Cisco access lists and OSPF network statements use wildcard masks.
Does this support IPv6?
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Not yet. This calculator handles IPv4 only, which is what most subnetting exercises, firewall rules, and cloud VPC planning still use.
Is my data uploaded anywhere?
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No. The math runs in your browser, so the addresses you type never leave your device.
Calculate a subnet now
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