CIDR / Subnet Calculator
Enter an IPv4 address in CIDR form to get the network, broadcast, masks, host range and host count. Nothing is uploaded — the maths runs locally.
CIDR / Subnet Calculator
CIDR (Classless Inter-Domain Routing) writes a network as an address plus a prefix length, such as 192.168.1.0/24. The prefix tells you how many bits are the network; the rest address hosts. This tool turns that into the fields you usually need for configuration and troubleshooting.
What it works out
- Network and broadcast addresses.
- Netmask and wildcard mask.
- First and last usable host, and the host count.
- IPv4 only;
/31and/32are handled as special cases.
Frequently asked questions
What does this tool do?
It reads an IPv4 address in CIDR form, such as 192.168.1.0/24, and shows the network address, broadcast address, netmask, wildcard mask, the first and last host and the host count.
Is anything uploaded?
No. The calculation runs entirely in your browser.
Does it support IPv6?
No. This tool supports IPv4 only, which is stated on the page.
What happens with /31 or /32?
A /32 is a single host. A /31 is a point-to-point link with no conventional usable host range, and the tool says so.
Can I enter a subnet mask instead of a prefix?
Yes. You can enter the prefix length, or a dotted-decimal subnet mask such as 255.255.255.0.
What does the slash value mean?
The number after the slash shows how many bits belong to the network prefix; the remaining bits address hosts within the subnet.
Related: the query string parser and chmod calculator, or browse every browser-only tool on the all tools page.