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Subnet Calculator

IPv4 + CIDR to network address, broadcast address, and usable host range.

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Subnet Details
IP Address192.168.1.10
CIDR Notation192.168.1.10/24
Subnet Mask255.255.255.0
Wildcard Mask0.0.0.255
Network Address192.168.1.0
Broadcast Address192.168.1.255
First Usable Host192.168.1.1
Last Usable Host192.168.1.254
Total Hosts256
Usable Hosts254
IP ClassC
Private / PublicPrivate

Every Field a Network Task Needs

Enter an address and drag the CIDR slider to see the network address, broadcast address, subnet mask, wildcard mask, and the actual first/last usable host — the complete set of numbers most subnetting tasks need, computed instantly with pure bitwise math and no server round-trip.

How to Use This Tool

  1. 1Enter an IPv4 addressAny address in the subnet you're working with.
  2. 2Set the CIDR prefixDrag the slider from /0 to /32 — the subnet details update live.
  3. 3Read the resultsNetwork address, broadcast address, subnet mask, and the usable host range.

Good to Know

  • The network and broadcast addresses are never usable for a host — they identify the subnet itself and the subnet's broadcast target, respectively.
  • A /31 network is a special case (point-to-point links) where both addresses are treated as usable, since there's no room for a separate network/broadcast pair — this tool handles that case correctly rather than showing zero usable hosts.
  • Private IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) are flagged directly in the results, since it's a common thing to double-check when configuring internal networking.
  • This tool covers IPv4 only — IPv6 subnetting uses a substantially different addressing scheme and isn't covered here.

Frequently Asked Questions

What's the difference between a subnet mask and CIDR notation?

They express the same thing two ways — a CIDR prefix like /24 is shorthand for the subnet mask 255.255.255.0. This tool shows both so you can use whichever your particular router or config format expects.

Why are only 254 of 256 addresses usable in a /24?

The first address in any subnet (all host bits zero) is reserved as the network address, and the last (all host bits one) is reserved as the broadcast address — neither can be assigned to a device.

What does the wildcard mask get used for?

It's the inverse of the subnet mask, used in some router configuration syntaxes (notably Cisco ACLs) instead of a standard subnet mask.

Is this free to use?

Yes, completely free, with no limit on how many calculations you run.