CIDR & Subnet Calculator for IPv4 and IPv6
Type 10.0.0.0/16, an IP with a mask or a range. Get every detail, split it, plan subnets and check AWS/Azure/GCP usable IPs.
Help shape CIDR & Subnet Calculator for IPv4 and IPv6
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Frequently Asked Questions
254. A /24 has 256 addresses; the network and broadcast addresses aren't usable. /31 and /32 are special cases that use every address.
AWS reserves 5 addresses per subnet, so a /24 gives 251 usable IPs. Azure also reserves 5 and Google Cloud 4.
The inverse of the subnet mask, used by Cisco ACLs and OSPF. For 255.255.255.0 it's 0.0.0.255.
Yes. Paste them into CIDR list tools and choose Summarize to get the fewest blocks covering the same addresses.
Yes — prefix details, compression, reverse ip6.arpa zones and subnet splitting for any prefix.
No. All calculations run in your browser; nothing is sent anywhere.