CIDR / Subnet Calculator
Enter an IPv4 CIDR block to instantly see its network and broadcast address, subnet mask, usable host range and host count.
- Network address
192.168.1.0 - Broadcast address
192.168.1.255 - Subnet mask
255.255.255.0 - Wildcard mask
0.0.0.255 - Usable host range
192.168.1.1 – 192.168.1.254 - First usable host
192.168.1.1 - Last usable host
192.168.1.254
Calculated entirely in your browser — nothing is sent to a server.
From CIDR to a full network picture
Type a block like 10.0.0.0/16 and this calculator expands it into everything you need to configure or document a network: the network address and broadcast address, the subnet mask and its wildcard counterpart, the first and last usable host, and the exact count of total and usable addresses. It also flags the classical address class, handy when you're reasoning about legacy ranges.
Why subnetting still matters
Whether you're carving a VPC into subnets, sizing a Kubernetes pod CIDR, or writing a firewall rule, getting the boundaries right avoids overlapping ranges and wasted address space. The calculator does the bit-shifting for you so you don't have to convert masks to binary by hand — pick a prefix, read the range, and move on. Everything runs locally, so you can plan private ranges without sending them anywhere.
FAQ
What does the /24 in a CIDR block mean?
The number after the slash is the prefix length — how many leading bits are fixed as the network portion. /24 fixes the first 24 bits, leaving 8 bits (256 addresses) for hosts. A larger prefix like /30 means a smaller network; a smaller prefix like /16 means a larger one.
Why are there fewer usable hosts than total addresses?
In a normal subnet the first address is the network address and the last is the broadcast address, so both are unusable for hosts. That's why a /24 has 256 total addresses but 254 usable. The exceptions are /31 (2 usable, point-to-point per RFC 3021) and /32 (a single host).
What's the difference between the subnet mask and the wildcard mask?
The subnet mask (e.g. 255.255.255.0) marks the network bits with 1s; the wildcard mask is its bitwise inverse (0.0.0.255) and marks the host bits. Wildcard masks are what ACLs in Cisco IOS and similar systems expect.
Does this calculator support IPv6?
This tool focuses on IPv4. IPv6 uses the same CIDR notation but 128-bit addresses and different reserved-address rules, so it needs a dedicated calculator.
Is my input sent to a server?
No. The entire calculation is bitwise math done in your browser — nothing is transmitted, so you can plan internal network ranges privately.
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