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🌐 Subnet / CIDR Calculator
Enter a CIDR notation like 10.0.0.0/16 — we compute the network address, broadcast address, subnet mask, host range (first/last usable), and total number of hosts. Useful for network engineers and cloud VPC planning.
Examples
192.168.1.0/24Mask 255.255.255.0 · 254 hosts · 192.168.1.1 – 192.168.1.25410.0.0.0/16Mask 255.255.0.0 · 65,534 hosts · 10.0.0.1 – 10.0.255.254172.16.0.0/302 usable hosts (point-to-point links)Frequently asked questions
What does /24 mean?
The first 24 bits identify the network; the remaining 8 bits identify hosts. /24 = 256 addresses (254 usable). /16 = 65,536. /30 = 4 (2 usable).
Why are 2 addresses unusable?
The first address (network) and last (broadcast) are reserved. Exceptions: /31 and /32 are special and treat both addresses as usable for point-to-point links.
How do AWS / GCP / Azure pick CIDR ranges?
They reserve a few addresses inside each subnet for the cloud provider (router, DNS, etc.). AWS reserves 5; subtract those from "usable" when planning.
About this tool
Subnet / CIDR Calculator runs entirely in your browser using standard Web APIs. No data is sent to any server. The source for this tool is in our public GitHub repository.
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Why this tool
vs typical free web-tool sites
| 1vw | Typical free site | |
|---|---|---|
| Price | Free | Free |
| Signup required | No | Often (for premium features) |
| Ads inside the tool | No | Yes (banner + video) |
| Data sent to server | No (browser-only) | Yes (inputs analyzed for ads) |
| Total tools | 96 | Often <20 or scattered across sites |
| Bookmarkable URL per tool | Yes | Mixed |
| Loads in under 1s | Yes (static) | Often slow (ad tracking) |
| Multilingual | EN / ES / PT / FR / DE | Usually EN only |
| Open source | Yes | No |