IPv4 Subnet Calculator
Enter an IPv4 address and CIDR prefix to get the network, broadcast, netmask, wildcard, usable host range, host count, and address class — computed instantly in your browser.
Subnet details
- Network address
- 192.168.1.0
- Broadcast address
- 192.168.1.255
- Netmask
- 255.255.255.0
- Wildcard mask
- 0.0.0.255
- First usable host
- 192.168.1.1
- Last usable host
- 192.168.1.254
- Total addresses
- 256
- Usable hosts
- 254
- CIDR
- /24
- Class
- C
About this tool
A subnet calculator turns an IP address plus a CIDR prefix (like 192.168.1.10/24) into every derived value a network engineer needs: the network address, the broadcast address, the subnet and wildcard masks, the first and last usable host addresses, and the total and usable host counts. It works by treating the address as a 32-bit unsigned integer and applying the mask with bitwise operations, so the results are exact rather than estimated. The tool also flags the classful range (A/B/C/D/E) the address falls in. Everything runs locally in your browser — no address you enter ever leaves the page — which makes it safe to use on internal or production network ranges. Edge cases follow the standards: a /31 is treated as an RFC 3021 point-to-point link with two usable addresses, and a /32 describes a single host.
How to use it
- Type an IPv4 address such as 10.0.0.5.
- Pick the CIDR prefix (/0 to /32) from the dropdown.
- Read the network, broadcast, mask, and host range from the results.
- Use the copy button to grab all values at once.
Frequently asked questions
- What is the difference between the network and broadcast address?
- The network address is the lowest address in the subnet (all host bits 0) and identifies the subnet itself; the broadcast address is the highest (all host bits 1) and reaches every host on the subnet. Neither is assignable to a normal host, which is why a /24 has 256 total addresses but only 254 usable hosts.
- How is the usable host count calculated?
- For a prefix of /30 or shorter it is 2^(32 − prefix) − 2, subtracting the network and broadcast addresses. A /31 is a special point-to-point case (RFC 3021) with 2 usable addresses and no broadcast, and a /32 is a single host.
- What is a wildcard mask?
- The wildcard mask is the bitwise inverse of the subnet mask (e.g. 0.0.0.255 for a /24). It is used in access-control lists on Cisco and other gear, where a 1 bit means "ignore this bit" when matching.
- What do the address classes A through E mean?
- They are the legacy classful ranges based on the first octet: A is 0–127, B is 128–191, C is 192–223, D (224–239) is multicast, and E (240–255) is reserved. Modern routing is classless (CIDR), but the class is still a useful sanity check.
- Does this tool send my IP addresses anywhere?
- No. All computation happens in your browser with JavaScript bitwise math. Nothing you type is transmitted, logged, or stored, so it is safe for internal and production ranges.
- Why does a /24 have 256 addresses but 254 hosts?
- A /24 leaves 8 host bits, giving 2^8 = 256 total addresses. Two of those — the network address and the broadcast address — are reserved, leaving 254 that can be assigned to actual devices.