Understanding Binary Numbers

Let’s be honest — for many systems and network administrators, binary numbers sit firmly in the “necessary evil” category.

Mention binary in a room full of IT professionals and you’ll often get eye-rolls, groans, or flashbacks to subnetting exams and vendor certifications. Some might even joke about arithmophobia — the irrational fear of numbers — and honestly, that reaction isn’t entirely unjustified.

But here’s the uncomfortable truth:

Without binary, computers, networks, IP addressing, routing, and security simply wouldn’t exist.

Every packet you route, every firewall rule you configure, every subnet you design — all of it ultimately resolves down to binary decisions. You don’t need to love binary, but if you work in IT, you absolutely need to understand it.

This article breaks binary down in a practical, IT-focused way — not as abstract maths, but as a tool you actually use, whether you realise it or not.

What Is Binary? (And Why Computers Use It)

Binary is known as a Base-2 numbering system. Unlike the decimal system (Base-10), which uses ten digits (0–9), binary uses only two values:

• 0
• 1

That’s it.

This simplicity is exactly why binary is so powerful in computing.

Binary and Electronics: The Real Reason It Exists

At the hardware level, computers don’t understand numbers — they understand electrical states.

• 1 typically represents on, true, or high voltage
• 0 represents off, false, or low voltage (ground)

Digital electronics are extremely good at reliably detecting these two states. Trying to represent ten different voltage levels (like decimal) would be unreliable, noisy, and expensive. Two states? Rock solid.

That’s why CPUs, RAM, storage, and network hardware all operate using binary logic.

Binary as a Language of Decisions

One of the most overlooked aspects of binary is that it isn’t just about numbers — it’s about decisions.

Binary underpins:

• Boolean logic (true/false)
• Access control decisions
• Firewall allow/deny rules
• Routing paths
• Subnet membership

In networking especially, binary is constantly answering yes/no questions:

• Is this IP in this subnet?
• Does this packet match this ACL?
• Should this bit be set or cleared?

Once you see binary as decision-making, not maths, it becomes far more intuitive.

How Binary Numbers Work

In binary, each position (or “bit”) represents a power of 2, starting from right to left.

Here’s how the first few binary positions break down:

Each time you move one place to the left, you double the value.

This is the exact same concept as decimal — except instead of powers of 10, you’re dealing with powers of 2.

Converting Binary to Decimal (The IT-Friendly Way)

To convert binary to decimal, follow one simple rule:

Add up the values of each position that contains a “1”. Ignore the zeros.

Example 1: Simple Conversion

Binary: 101

Break it down:

• 1 × 4
• 0 × 2
• 1 × 1

Result:
4 + 0 + 1 = 5 (decimal)

Example 2: A More Realistic Binary Number

Binary: 11110

Result:
16 + 8 + 4 + 2 = 30 (decimal)

Example 3: Common in Networking

Binary: 10001

• 16 + 1 = 17 (decimal)

This kind of pattern shows up constantly when dealing with subnet masks and IP ranges.

Breaking Down a Full 8-Bit Binary Number

Let’s take a number you’ll often see in networking:

Binary: 11001000

Here’s how it breaks down:

Add up the “1” values only:

128 + 64 + 8 = 200 (decimal)

If you’ve ever wondered why IP addresses go up to 255 — this is why. An 8-bit binary number maxes out at:

128 + 64 + 32 + 16 + 8 + 4 + 2 + 1 = 255

Why Binary Is Critical in Networking (Not Just Theory)

Many binary tutorials stop at conversions — which is where they fail IT professionals.

Binary and IP Addressing

Every IPv4 address is actually:

• 32 bits
• Split into four 8-bit octets

Example:

192.168.1.10

Each of those numbers is just a binary value converted to decimal for human readability.

Subnetting? That’s pure binary masking.
CIDR notation? Binary bit boundaries.
Routing decisions? Binary comparisons.

If you understand binary, subnetting stops being memorisation and starts making sense.

The below binary number of 11001000 can be explained easily using the below table.

Binary in the Real World: Why This Knowledge Saves Time

In real IT environments, binary understanding helps you:

• Quickly validate subnet ranges
• Spot misconfigured IP addresses
• Understand why routes overlap
• Diagnose firewall rule mismatches
• Make sense of ACL and mask logic

I’ve seen countless troubleshooting sessions drag on for hours because someone was blindly following subnet “rules” they didn’t actually understand.

Binary knowledge turns guesswork into confidence.

You Don’t Need to Be a Maths Genius

Here’s the good news:
You don’t need to calculate binary conversions in your head every day.

But you do need to:

• Understand what the bits represent
• Know how binary scales
• Recognise patterns when troubleshooting

Think of binary like knowing how an engine works — you don’t rebuild it daily, but understanding it helps you diagnose problems faster.

Final Thoughts: Binary Is a Skill, Not a Party Trick

Binary isn’t there to torture IT professionals or make certifications harder. It’s the foundation language of computing and networking.

Once you stop treating it as abstract maths and start viewing it as:

• Electrical states
• Logical decisions
• Network boundaries

…it becomes far less intimidating — and far more useful.

If you work in IT and networking, understanding binary isn’t optional. It’s one of those quiet skills that separates someone who configures systems from someone who truly understands them.

Daniel Lutton

From my early days on the helpdesk through roles as a service desk manager, systems administrator, and network engineer, I’ve spent more than 25 years in the IT world. As I transition into cyber security, my goal is to make tech a little less confusing by sharing what I’ve learned and helping others wherever I can.