CIDR / subnet calculator
Network range, usable hosts (including Azure’s 5 reserved addresses) and subnet splits.
Runs locally. Nothing you paste leaves this tab.
Subnets
Why “usable in Azure” is smaller
Azure reserves five addresses in every subnet: the network address, the first three host addresses (gateway and DNS) and the broadcast address. A /29 gives you 3 usable IPs in Azure, not 6. AWS also reserves five per subnet.