Loading page content
Enter a CIDR block and get the network address, broadcast address, usable host range, total host count, subnet mask, wildcard mask, and IP class. Everything you need to size a VPC subnet or write a security group rule.
Enter a CIDR block to calculate network address, broadcast address, host range, subnet mask, and usable host count.
Subnet math is easy to get wrong by one bit and expensive to get wrong in production. The two numbers that matter for cloud work are usable hosts and the boundary: AWS reserves five addresses per subnet, not two, so a /28 gives you eleven usable IPs rather than fourteen. Azure reserves five as well. Plan with that in mind or your first autoscaling event will fail on address exhaustion.
The wildcard mask output is there for ACLs and OSPF configuration, where Cisco-style syntax wants the inverted mask. It is the one field people forget how to compute under time pressure.