Tool
Subnet Calculator
Calculate network address, broadcast address, usable host range, and subnet mask from an IPv4 CIDR, runs entirely in your browser.
Updated Jul 24, 2026Victor Nwoke
About this tool
Enter an IPv4 address in CIDR notation (for example 10.0.0.0/24) and get the network address, broadcast address, subnet mask, usable host range, and host count. The math runs locally in your browser.
This is the calculation behind every VNet, VPC, and on-premises network plan: how big is this block, where does it end, and does it overlap the next one. Overlapping address space is one of the most expensive mistakes in cloud networking because peerings and VPNs between overlapping ranges simply cannot be built, and fixing it later means re-addressing live workloads.
Frequently asked questions
- What does the /24 style prefix actually mean?
- The number after the slash is how many leading bits of the address are fixed as the network portion. A /24 fixes 24 bits, leaving 8 for hosts (256 addresses); each step smaller doubles the block, so a /23 holds 512 and a /16 holds 65,536. Smaller prefix number, bigger network.
- Why are there 2 fewer usable hosts than addresses?
- The first address in a subnet identifies the network itself and the last is the broadcast address, so a /24 has 254 usable hosts, not 256. Cloud platforms reserve more: Azure and AWS each take the first four addresses plus broadcast, so a /24 there yields 251.
- Which private ranges should I plan with?
- RFC 1918 reserves 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 for private use. Cloud networks almost always carve from these. Plan blocks deliberately (say, one /16 per environment, split into /24s per subnet) and document them, so future peerings do not collide.
Continue learning
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