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Subnet Mask Converter

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Convert subnet masks, CIDR prefixes and wildcard masks; calculate network, broadcast and host ranges; and split a large network into equal subnets or VLAN-sized blocks (VLSM).

Convert a mask or prefix

/24 · 24 · 255.255.255.0 · 0xFFFFFF00 · wildcard 0.0.0.255 · 192.168.1.10/24 · 192.168.1.10 255.255.255.0

Try:

Mask & network

IPv4 prefix reference (/0 – /32)

Split a network

Divide a large network into smaller subnets, e.g. for VLANs. Equal-size split, or VLSM sizing per VLAN.

How to split

How it works

An IPv4 subnet mask is 32 bits: the leading 1-bits mark the network part, and their count is the CIDR prefix (/24 = 255.255.255.0). The wildcard mask is its inverse. Splitting a network borrows host bits: each extra prefix bit doubles the number of subnets and halves their size. VLSM gives each subnet only the size it needs, allocating the largest first so every block stays aligned.

Terms

  • Network address: the first address (all host bits 0); it names the subnet.
  • Broadcast address: the last address (all host bits 1); traffic to it reaches every host. Not used in /31 and /32.
  • Host range: the addresses you can assign to devices — between network and broadcast address.
  • Wildcard mask: the inverted mask (0.0.0.255 for /24), used in Cisco ACLs and OSPF network statements.
  • IPv6 uses prefix lengths only — no masks, no broadcast — and LAN subnets are normally /64. For full IPv6 ranges use the Subnet Calculator.

Frequently asked questions

Why does a /24 have 254 usable hosts, not 256?

In a classic IPv4 subnet the first address identifies the network and the last is the broadcast address. /31 (point-to-point links, RFC 3021) and /32 (a single host) are exceptions: all their addresses are usable.

How do I split a /16 into 100 networks?

You need 7 extra prefix bits (2⁷ = 128 ≥ 100), so each subnet is a /23 with 510 usable hosts; 28 of the 128 blocks stay free for later.

Does IPv6 use subnet masks?

No. IPv6 networks are written with a prefix length only (e.g. 2001:db8::/48), there is no broadcast address, and LAN subnets are normally /64.