🌐IPv4 / CIDR Subnet Calculator
From CIDR notation (e.g., 192.168.0.0/24), calculate the network address, broadcast, subnet mask, and usable hosts. Useful for designing internal networks, splitting AWS VPC subnets, writing firewall rules, and networking exam prep.
How to use
- 1Enter an IPv4 address and prefix length (e.g., 192.168.0.0/24).
- 2Results display instantly.
FAQ
Does it support IPv6?+
IPv4 only for now. IPv6 CIDR (/64 etc.) needs a separate tool.
What is CIDR?+
Classless Inter-Domain Routing. 'IP-address/prefix-length' notation for subnets. /24 means the upper 24 bits are the network and the remaining 8 are hosts.
How many hosts in /24?+
256 addresses minus network and broadcast = 254 usable. /16 has 65,534, /20 has 4,094.
Common CIDRs in AWS VPC?+
VPCs often start at /16 (65,534 IPs) with /24 (254) subnets. AZs are sometimes split into /20.
Are there private IP ranges?+
10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 are private. Used in home and office networks.
How do I check if two CIDRs overlap?+
Compute each CIDR here and compare ranges, or use a dedicated 'subnet overlap' tool.