# Calculate IP Subnets

> IPv4 subnets from CIDR or dotted-decimal masks — network, broadcast, host range, binary/hex/integer IDs, reverse DNS, AWS/Azure/GCP usable host counts.

Live tool: https://lofttools.com/tools/dev-tools/ip-subnet-calculator

Category: Dev Tools

## How it works

1. **Enter IP and mask** — Paste an IPv4 address (network or host) and the subnet mask in CIDR (/24) or dotted-decimal (255.255.255.0) form.
2. **Read the core results** — Network, broadcast, subnet mask, wildcard, host range, class, and type appear instantly.
3. **Expand technical or cloud panels** — Open the Technical details panel for binary / hex / integer / reverse DNS values, or the Cloud panel for AWS / Azure / GCP usable host counts.

## FAQ

### What input formats does the mask field accept?

CIDR in either /24 or plain 24 form, the dotted-decimal subnet mask (255.255.255.0), and the inverse / wildcard mask (0.0.0.255) all resolve to the same prefix.

### How are /31 and /32 networks handled?

A /31 is treated as a point-to-point link per RFC 3021 — both addresses are usable, there is no dedicated broadcast. A /32 is a single host. Usable-host counts reflect these rules.

### Why do AWS, Azure, and GCP show fewer usable hosts than the raw total?

AWS and Azure reserve 5 addresses per subnet (network, gateway, one or two DNS/future, broadcast). GCP reserves 4 (network, gateway, second-to-last, broadcast). The Cloud panel subtracts these and flags subnets that are too small for each provider.

### What is the difference between subnet mask and wildcard mask?

The wildcard mask is the bitwise inverse of the subnet mask. Cisco ACLs and some routing protocols use wildcard form (e.g. 0.0.0.255) where the subnet mask would be 255.255.255.0.

### Can I paste a host address like 192.168.1.100/24?

Yes. Enter the host IP in the address field and /24 in the mask field — the tool derives the network (192.168.1.0), broadcast, and host range automatically and notes that a host address was detected.

## Privacy

This tool runs entirely in the browser. Files are not uploaded to a server. They never leave the user's device.

## More

- All tools: https://lofttools.com/tools
- Category: https://lofttools.com/tools/dev-tools
- LLM index: https://lofttools.com/llms.txt