Free IPv4 subnet / CIDR calculator — network, mask, host range and usable hosts

Network address192.168.1.0
Broadcast address192.168.1.255
Subnet mask255.255.255.0
Wildcard mask0.0.0.255
First usable host192.168.1.1
Last usable host192.168.1.254
Total addresses256
Usable hosts254
CIDR/24

IPv4 subnet math computed entirely in your browser — nothing is uploaded.

🌐 Subnet Calculator — Free Online Tool

Calculate IPv4 subnets from CIDR, free. CIDR notation (RFC 4632) writes an IPv4 network as an address plus a prefix length, like 192.168.1.0/24. This calculator expands a CIDR block into its network address, subnet mask, broadcast address, usable host range and host count — entirely in your browser.

🚀 Why use this Subnet Calculator tool?

It expands an IPv4 CIDR block into network, mask, broadcast, host range and usable-host count, so you can plan and verify addressing without manual binary math. 100% free, no registration, and complete privacy — everything runs locally in your browser, so your data never touches a server.

Key Features

🧮Full breakdown

Enter a CIDR like 10.0.0.0/24 and get network address, mask, broadcast, first/last host and total usable hosts.

🔢No binary by hand

The tool does the bitwise math for you, so you don't have to convert masks and addresses to binary.

🔒100% private

Calculation runs locally in your browser; nothing you enter is uploaded or stored.

🆓Free, no signup

Unlimited calculations with no account, on desktop and mobile.

Popular Use Cases

Network design

  • Plan VPC/VLAN subnets
  • Size address space
  • Avoid overlap

Cloud & DevOps

  • Define CIDR for VPCs
  • Set security-group ranges
  • Document IP plans

Troubleshooting

  • Find an address's network
  • Check host range
  • Verify a mask

What It Handles

Computes

  • Network & broadcast
  • Subnet mask & wildcard
  • Prefix /0–/32

Hosts

  • First & last usable host
  • Usable host count
  • Total addresses

Workflow

  • Enter CIDR
  • Instant result
  • Runs offline

Sources & References

Frequently Asked Questions

How do I calculate a subnet from CIDR?

Enter an IPv4 address with a prefix (e.g. 192.168.1.0/24). The tool applies the prefix as a mask to derive the network, broadcast, mask, host range, and number of usable hosts.

How many usable hosts are in a /24?

A /24 has 256 total addresses, but the network and broadcast addresses are reserved, leaving 254 usable hosts. In general a /n has 2^(32-n) addresses and 2^(32-n) − 2 usable hosts (for n ≤ 30).

What's the difference between the network and broadcast address?

The network address is the first address in the block (all host bits 0) and identifies the subnet; the broadcast address is the last (all host bits 1) and reaches every host. Neither is assigned to a device.

Is my input uploaded anywhere?

No. The calculation happens entirely in your browser; nothing you enter leaves your device.

Do /31 and /32 work?

Yes. /32 is a single host (used for routes/loopbacks) and /31 is a 2-address point-to-point link (RFC 3021) with no separate broadcast — the calculator handles these edge cases.

🎓 Pro Tips

  • Tip 1: Remember the −2 rule for usable hosts on /30 and larger (network + broadcast are reserved); /31 point-to-point links are the documented exception.
  • Tip 2: Plan subnets on power-of-two boundaries to avoid overlap and to keep room to grow without renumbering.
  • Tip 3: Standard: CIDR is defined in RFC 4632 — https://www.rfc-editor.org/rfc/rfc4632.