Learn it. Calculate it. Own it.

Subnet math without the mystery.

A friendly ELI10 walkthrough, a live calculator, and a fast-paced quiz arena that rewards real progress.

IPv4 only Earned crates No sign-in needed

ELI10 SUBNETTING

Think of an IP address like a street address.

There are four number boxes. A subnet mask tells us which boxes, and which parts of boxes, name the neighborhood.

The address

192.168.4.73

IPv4 is four numbers from 0 to 255. Together they identify one device, like a house number on a street.

The slash number

/ 24

The /24 says “the first 24 binary switches name the neighborhood.” The rest are available for houses.

The neighborhood

192.168.4.73

With /24, the first three boxes stay fixed. So 192.168.4.73 belongs to the 192.168.4.0 neighborhood.

THE ONE RULE TO REMEMBER

Hosts = 2^{host bits} − 2

The two special addresses are reserved: the network address is the neighborhood label, and the broadcast address talks to every house.

Example: /27 32 total addresses

32 − 2 = 30 usable hosts

FAST METHOD

The “jump size” trick

Do not convert every question to binary. Find the interesting octet, calculate its jump size, then round down.

1
Find the mask octet./27 means 255.255.255.224. The interesting number is 224.
2
Get the jump size.256 − 224 = 32. Networks start at 0, 32, 64, 96, 128...
3
Round down to the network.192.168.1.77 falls between 64 and 95, so its network is .64.
4
One less is broadcast.The next network starts at .96, so .95 is this subnet’s broadcast address.

CHEAT SHEET

Common subnet sizes

Prefix	Mask ending	Jump	Usable hosts
/24	0	256	254
/25	128	128	126
/26	192	64	62
/27	224	32	30
/28	240	16	14
/29	248	8	6
/30	252	4	2

READY TO PRACTICE?

Use the calculator once, then test your instincts.

LIVE TOOL

Subnet calculator

Enter any valid IPv4 address and CIDR prefix. Calculations happen entirely in your browser.

NETWORK ADDRESS 192.168.1.64 Mask: 255.255.255.224

Broadcast192.168.1.95

Usable hosts30

Host range192.168.1.65 – 192.168.1.94

Block size32

A /27 has 5 host bits: 2⁵ = 32 addresses. Its blocks jump by 32: 0, 32, 64, 96… and 77 lives in the 64–95 block.

QUIZ ARENA

Build your subnet instincts.

One focused question at a time. Correct answers build streaks, XP, and earned study crates.

SESSION SCORE 0

NETWORK ADDRESS

45s

STREAK0

For the address below, what is the network address?

192.168.1.77/27

TIP

For a network question, find the block where the final changing octet belongs. The first number in that block wins.

YOUR KIT

Study collection

Every crate is earned through correct answers. Contents are cosmetic badges and practical study boosts only.

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Total XP0

Questions answered0

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