Subnet Mask Calculator
Enter an IPv4 address with CIDR notation to find the netmask, network address, broadcast address, usable host range, and total host count.
Runs entirely in your browser. Your IP entry is never uploaded anywhere.
How to use this tool
This subnet calculator turns an IP address and a CIDR notation prefix into a full breakdown of the network. Type an IPv4 address such as 192.168.1.10 into the first box, then pick the CIDR prefix (for example /24) from the dropdown. Press Calculate and the tool shows the subnet mask, wildcard mask, network and broadcast address, the first and last usable host, and the total and usable host count. Use the Copy results button to put the whole table on your clipboard for documentation or a ticket.
How subnetting works
An IPv4 address is 32 bits long, written as four 8-bit numbers (octets) like 192.168.1.10. The CIDR prefix tells you how many leading bits belong to the network. A /24 means the first 24 bits are the network and the remaining 8 bits identify hosts. This IP address range finder works purely with bitwise math on those 32 bits.
The wildcard mask is simply the bitwise inverse of the subnet mask, which is what tools and access lists often use. For a /31 point-to-point link and a /32 single host, the "minus two" rule does not apply, so the network broadcast address calc treats those as special cases and reports the addresses directly.
A real example
Take the input 192.168.1.10/26. A /26 prefix gives 32 - 26 = 6 host bits, so the subnet mask is 255.255.255.192 and the wildcard mask is 0.0.0.63. The network address is 192.168.1.0 and the broadcast address is 192.168.1.63. The first usable host is 192.168.1.1 and the last is 192.168.1.62. That is 2^6 = 64 total addresses and 64 - 2 = 62 usable hosts. The address 192.168.1.10 falls inside that range, so it is a valid host on the subnet.
Common questions
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation writes a network as an IP address followed by a slash and the number of network bits, such as 10.0.0.0/8. This cidr notation tool converts that prefix into the matching dotted-decimal subnet mask and the full address range.
Why are two addresses unusable in most subnets?
The first address in a block is the network identifier and the last is the broadcast address, so neither can be assigned to a device. That is why a /24 has 256 total addresses but only 254 usable hosts. The exceptions are /31 (two usable hosts for point-to-point links) and /32 (a single host).
What is a wildcard mask used for?
A wildcard mask is the inverse of the subnet mask, where a 0 bit means "must match" and a 1 bit means "any value". Cisco access control lists and some routing configurations use wildcard masks instead of subnet masks, so the calculator shows both.
Does this work for any private or public IP?
Yes. The IP address range finder uses plain bitwise arithmetic on the 32-bit value, so it handles any valid IPv4 address from 0.0.0.0 to 255.255.255.255 with any prefix from /0 to /32, whether the address is private, public, or loopback.
Is my data sent to a server?
No. Everything is calculated locally in your browser with JavaScript. Nothing you type is uploaded, logged, or stored anywhere, so it is safe to use with internal network details.