Visual Subnet Calculator

Split and join subnets visually. Click a row to divide or merge.

🔢 Just need one CIDR's details? Try the CIDR Calculator →
Cloud Provider:
Show columns:

Cloud Reserved IP FAQ

How many IP addresses does AWS reserve in each VPC subnet?

AWS reserves 5 IP addresses in every VPC subnet: the network address (.0), the VPC router (.1), the DNS server (.2), a future-use address (.3), and the broadcast address (the last address in the block). A /24 subnet with 256 addresses therefore has 251 usable IPs.

How many IP addresses does Azure reserve in each subnet?

Azure reserves 5 IP addresses per subnet: the network address, the default gateway (.1), two addresses mapped for Azure DNS (.2 and .3), and the broadcast address (the last address in the block).

How many IP addresses does Google Cloud (GCP) reserve in each subnet?

Google Cloud reserves 4 IP addresses per subnet: the network address, the default gateway (.1), a second-to-last reserved address, and the broadcast address (the last address in the block).

Why do usable host counts differ between AWS, Azure and GCP for the same subnet size?

Each cloud provider reserves a different number of addresses in every subnet for its own networking services, such as the default gateway and DNS. Select a provider above and this tool automatically adjusts the usable host count and lists exactly which addresses are reserved and why.