You've probably seen the little sticker on your new laptop. It screams 1TB SSD like a badge of honor. You get home, plug it in, and Windows tells you that you actually have 931 gigabytes. It feels like a scam. It's not. But honestly, the way manufacturers and operating systems talk to each other is basically a giant game of "lost in translation."
So, how many gig in a terabyte?
If you want the quick, "marketing" answer, it's 1,000. If you want the technical, "binary" answer that your computer actually uses, it's 1,024. This discrepancy is the reason your "Terabyte" drive always looks smaller than advertised the second you turn it on. It’s a mess of decimal versus binary math that has existed since the 1970s.
Why the Number of Gigabytes Changes Depending on Who You Ask
The confusion stems from two different systems of measurement: the International System of Units (SI) and the binary system.
In the SI system—the one we use for meters and liters—the prefix "kilo" means 1,000. "Mega" means a million. "Giga" means a billion. Following this logic, a terabyte is exactly 1,000 gigabytes. Hard drive manufacturers like Western Digital and Seagate love this system. Why? Because it makes their numbers look bigger. If you sell a drive as 1,000,000,000,000 bytes, you can call it a Terabyte.
Computers don't think in base 10. They think in base 2.
Because electricity is either on or off, computers calculate everything in powers of two. To a computer, a "kilo" isn't 1,000; it's $2^{10}$, which is 1,024. When you scale that up, a megabyte is 1,024 kilobytes, a gigabyte is 1,024 megabytes, and a terabyte is 1,024 gigabytes.
When you ask how many gig in a terabyte, you're caught between these two worlds. macOS (since Snow Leopard) actually switched to the decimal system to match the stickers on the boxes. If you buy a 1TB drive and plug it into a Mac, it says 1TB. Windows, however, still uses binary but insists on calling them "GB" instead of the technically correct "GiB" (Gibibytes). It’s annoying.
The Math Breakdown
Let’s look at the actual numbers. If we are talking about Decimal (SI) units, which is what you see on a retail box:
- 1 Kilobyte (KB) = 1,000 Bytes
- 1 Megabyte (MB) = 1,000 KB
- 1 Gigabyte (GB) = 1,000 MB
- 1 Terabyte (TB) = 1,000 GB
Now look at the Binary (JEDEC/IEC) units, which is what Windows uses:
- 1 Kibibyte (KiB) = 1,024 Bytes
- 1 Mebibyte (MiB) = 1,024 KiB
- 1 Gibibyte (GiB) = 1,024 MiB
- 1 Tebibyte (TiB) = 1,024 GiB
When Windows shows you "931 GB," it's actually showing you 931 Gibibytes. The "lost" 69 gigabytes didn't vanish into thin air. They are just being measured with a larger yardstick.
Real World Examples: What Can You Actually Fit in 1,000 Gigabytes?
Numbers are abstract. Let's get real. A terabyte is a massive amount of space, but it’s shrinking every year as file sizes explode.
Take gaming. In 2010, a big game was 10GB. Today? Call of Duty: Black Ops 6 or Ark: Survival Ascended can easily swallow 200GB to 300GB of space. On a 1TB drive, you’re looking at maybe four or five massive AAA titles before you’re hitting the "Delete" key to make room for a patch.
Photos are a different story. If you’re a casual smartphone photographer, a 12MP JPEG is roughly 3MB to 5MB. You could fit roughly 200,000 to 300,000 photos in a terabyte. But if you’re a pro shooting 45MP RAW files on a Sony A7R V? Those files are 60MB+ each. Suddenly, that terabyte only holds about 16,000 images. Still a lot, but a far cry from "infinite."
Video is the real storage killer. 4K video at 60fps can eat up 400MB per minute of footage. If you’re a YouTuber or a hobbyist editor, a 1TB drive is basically just a temporary workspace. You’ll fill it in a few days of heavy shooting.
The Crucial Difference Between Capacity and Useable Space
It’s not just the decimal-to-binary conversion that steals your space.
When you format a drive, the file system itself (NTFS for Windows, APFS for Mac) requires a "map" to keep track of where files are. This is called metadata. This overhead takes up a small percentage of the drive. Then there's the "hidden" partition. Most modern PCs come with a recovery partition—usually 500MB to 15GB—that contains the tools to reinstall your OS if things go sideways.
You also have to consider SSD health.
Solid State Drives shouldn't actually be filled to 100%. Most experts, including engineers at Samsung and Crucial, recommend keeping about 10% to 20% of the drive empty. This allows for "wear leveling." The drive needs empty blocks to move data around so the flash memory cells don't wear out unevenly. If you fill a 1TB drive to 999GB, it will slow down significantly. Its lifespan will drop too.
How to Choose the Right Size: Is 1TB Enough in 2026?
Honestly, 1TB is currently the "bare minimum" for a primary computer.
✨ Don't miss: Should You Team Up With Candela or Arlo? The Honest Truth About Your Smart Home Ecosystem
If you are a student or an office worker using Google Docs, 1TB is overkill. You’ll never fill it. 256GB is plenty. But for everyone else, the math is changing. 4K streaming, high-res phone backups, and massive software suites mean that 512GB fills up in the first six months.
Cloud storage is the "hidden" gigabyte. Most people pay for 200GB of iCloud or 2TB of Google One. This creates a hybrid environment. Your local drive might only have 500GB, but your "files" total 3TB. When you're calculating how many gig in a terabyte you need, look at your "Data Gravity"—how much stuff you must have access to without an internet connection.
Summary of Practical Steps for Managing Your Terabytes
Stop guessing and start measuring. If you’re constantly running out of space, don't just buy a bigger drive. Check your "temp" folders. Windows "Disk Cleanup" is okay, but tools like WizTree or WinDirStat are better. They give you a visual map of every single gigabyte. You’ll often find that a forgotten video cache or a 2-year-old game install is hogging 100GB.
If you are buying new hardware, always do the "Windows Tax" math. Multiply the advertised size by 0.93. That is your actual useable space in binary.
- 500GB advertised = ~465GB useable
- 1TB advertised = ~931GB useable
- 2TB advertised = ~1.86TB useable
The most cost-effective way to get more gigabytes today isn't internal storage. It's external NVMe enclosures. You can buy a high-speed 2TB M.2 drive and a USB-C enclosure for significantly less than what Apple or Dell charges for a factory upgrade.
Understand that a "Gigabyte" isn't a fixed unit across the industry. It’s a marketing term for 1,000,000,000 bytes and a technical term for 1,073,741,824 bytes. Know which one you're looking at before you spend the money.
Verify your current storage usage by hitting Windows Key + E, right-clicking your C: drive, and selecting Properties. Compare that to the box your computer came in. Now you know where those "missing" gigabytes went.