You just bought a shiny new external drive. The box says 1 TB in massive, bold letters. You plug it into your Windows PC, right-click "Properties," and suddenly, you're looking at something like 931 GB.
Wait. Where did the rest go?
Did the manufacturer rip you off? Is the drive broken? Honestly, it’s one of the most frustrating things about tech today. The answer to how many gb is in 1 tb depends entirely on who you ask—a mathematician or your computer’s operating system.
Usually, the short answer is 1,000 GB. But if you’re looking at your screen, the answer feels more like 1,024. Or less. It’s a mess of marketing math versus binary reality.
✨ Don't miss: How to Go on YouTube: What Most People Get Wrong About Getting Started
The Great Math War: Decimal vs. Binary
The reason you're seeing different numbers comes down to two different systems of measurement: the International System of Units (SI) and the binary system.
Disk manufacturers love the decimal system. It makes numbers look bigger. In their world, 1 Kilobyte is 1,000 bytes. Simple, right? You just keep adding zeros.
1,000 Kilobytes = 1 Megabyte.
1,000 Megabytes = 1 Gigabyte.
1,000 Gigabytes = 1 Terabyte.
But computers don't think in base-10. They think in bits and bytes—on or off. They use base-2. For a computer, a Kilobyte is actually $2^{10}$ bytes, which equals 1,024. This small 24-byte difference doesn't seem like much when you're talking about a text file from 1995. However, as you scale up to Gigabytes and Terabytes, that "small" difference compounds into a massive gap.
By the time you hit a Terabyte, you’re losing about 7% of the advertised space to this mathematical discrepancy. Windows still uses binary to calculate space but labels it as "GB," which is technically incorrect based on modern standards. They should probably call them "GiB" or Gibibytes, but nobody wants to say that out loud at a dinner party.
Why your drive looks "small" the moment you plug it in
If you want to know how many gb is in 1 tb on a practical level, you have to account for the "Formatting Tax."
🔗 Read more: Why the 35w dual usb c port power adapter is actually the only charger most people need
When you buy a drive, it’s a blank slate. To actually put files on it, the drive needs a filing system. Think of it like a library. You can have a massive building, but if you don't have shelves, aisles, and a card catalog, you just have a pile of books on the floor.
File systems like NTFS (Windows), APFS (Mac), or exFAT take up physical room. They create a directory structure so the OS knows exactly where your 4K video of your cat is located. This "overhead" eats into your usable space.
So, you start with 1,000,000,000,000 bytes (1 TB).
Windows converts that to binary ($1,000,000,000,000 / 1024 / 1024 / 1024$), which brings you down to roughly 931 GB.
Then, the file system takes its cut.
Suddenly, your "Terabyte" drive has about 915 to 920 GB of actual, usable space for your games and photos.
It feels like a scam. It's not. It's just engineering.
Real-world capacity: What can you actually fit?
Let's stop talking about bits for a second and talk about stuff. If you have roughly 931 GB of usable space on a 1 TB drive, what does that actually look like in 2026?
- Video Games: This is where it gets depressing. Modern AAA titles like Call of Duty or the latest Grand Theft Auto can easily exceed 150 GB or even 200 GB with high-res texture packs. On a 1 TB drive, you might only fit five or six "prestige" games before you're deleting things to make room.
- Photography: If you're a pro shooting uncompressed RAW files on a 45MP camera, a single photo can be 50 MB. You're looking at about 18,000 photos. Sounds like a lot, until you go on a two-week safari.
- Video: 4K video at 60fps is a storage killer. You’re looking at roughly 42 GB for every hour of footage. A 1 TB drive gives you about 22 hours of high-quality 4K video.
If you're just storing Word docs and spreadsheets? You'll never fill it in your lifetime. But for most of us, 1 TB is the new "minimum" rather than "plenty."
The "Hidden" Partition Problem
Sometimes, the number of GB in your TB looks even lower because of recovery partitions.
If you bought a pre-built laptop from Dell, HP, or Apple, the manufacturer often hides a "ghost" portion of the drive. This contains a backup of your operating system. If your computer crashes, you use this hidden data to factory reset. You can't see this space in your file explorer, but it's there, eating up 10 to 20 GB of your Terabyte.
You can technically delete these partitions using Disk Management tools, but honestly? Don't. Unless you have a physical recovery USB ready to go, that "lost" space is your insurance policy.
The Gibibyte Controversy
In 1998, the International Electrotechnical Commission (IEC) tried to fix this mess. They decided that "Giga" should strictly mean 1,000, and they invented "Gibi" to mean 1,024.
So, technically:
1 Terabyte (TB) = 1,000 Gigabytes (GB)
1 Tebibyte (TiB) = 1,024 Gibibytes (GiB)
Apple actually listened. If you use a modern Mac (macOS Snow Leopard or later), Apple calculates storage using the decimal system. If you buy a 1 TB drive and plug it into a Mac, it will actually show you 1 TB of space. Apple basically decided to change the way the computer counts so that it matches the marketing on the box.
Windows, being the stubborn veteran of the tech world, refused to change. This is why the same USB drive looks "bigger" on a Mac than it does on a PC. The data is the same; the ruler used to measure it is different.
Practical Steps for Managing Your Terabyte
Knowing how many gb is in 1 tb is one thing, but managing it is another. Since you now know you're starting with about 931 GB of binary space, you need to be smart.
First, check your "Other" storage. On both Windows and Mac, temporary files and "system data" can bloat over time. Use a tool like WinDirStat or DaisyDisk to see a visual map of your drive. Sometimes a forgotten "Downloads" folder is holding 50 GB of installers you don't need anymore.
Second, understand that SSD performance can actually drop if you fill them to the absolute brim. Solid State Drives need a little "breathing room" (called over-provisioning) to move data around and keep the drive healthy. Try to keep at least 10% of your 1 TB drive empty. If you cross that 900 GB mark, you might notice your system start to stutter.
Third, look at the Cloud. If you’re constantly hitting the limit of your 1 TB drive, you don't necessarily need a 2 TB drive. Offloading cold storage—stuff you don't look at daily—to Google Drive or iCloud can free up that precious local GB for apps that actually need the speed of your local SSD.
Actionable Takeaways
- Always assume you're getting 931 GB: When buying a drive for a Windows machine, ignore the "1 TB" label and do your math based on the lower binary number.
- Check the File System: If you're moving files between Mac and PC, use exFAT. It's the most compatible, though it has slightly more overhead than the native formats.
- Don't panic about "missing" space: It’s almost never a hardware flaw. It’s just the difference between base-10 marketing and base-2 computing.
- Monitor your SSD health: Use tools like CrystalDiskInfo to make sure that as you fill those hundreds of Gigabytes, your drive isn't wearing out prematurely.
The mystery of the missing Gigabytes isn't really a mystery once you realize that "1,000" and "1,024" have been fighting for dominance since the 1970s. Just remember: the bigger the drive, the bigger the "loss" you'll see on your screen. If you ever move up to a 10 TB drive, you'll "lose" almost an entire Terabyte just to math. Be prepared for it.