Subnet Calculator — IPv4 / IPv6 CIDR

Compute network, mask, wildcard, usable hosts, and address class for IPv4 or IPv6. Fully local.

IP address

Prefix

Mode

Count

Binary

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Result

Enter an address and prefix.

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Subnet calculator

Two fields: IP address (no /) and prefix (length or IPv4 mask). Shows network, hosts, and class — not cloud reserved ranges.

Developer notes

• Address without a slash — “/24” in the address field is an error. • Mask mode is IPv4-only. • IPv4 /31 = 2 hosts (RFC 3021); /32 = 1. • IPv6: usable = total; no L2 broadcast. • 64 KiB limit.

Options

Prefix mode

cidr = length /24; mask = IPv4 dotted mask (255.255.255.0).

Show binary

Adds binary fields for address / network / mask (IPv4).

Host count style

usable (IPv4 rules; IPv6 equals total) or total = 2^(host bits).

When teams pick this route

• Check an addressing plan before deploy. • Compare usable vs total. • Show binary view to debug a mask.

Worked examples

IPv4 /24

Before

192.0.2.10

After

network 192.0.2.0 · broadcast 192.0.2.255 · usable 254

IPv6 /64

Before

2001:db8::1

After

network 2001:db8:: · last address in /64 · no L2 broadcast

Related networking tools

Hub networking tools. For numeric base conversion: number-base-converter.

Subnet calculator FAQ

Local IPv4 / IPv6 CIDR

When should I use the number-base converter instead?

To convert an integer between bases 2–36 (hex of a number, binary of a value), use number-base-converter. Networking tools compute subnets and CIDRs — not general base conversion.