You're looking at your phone storage, and it says you've got 2 GB left. You try to download a 2,000 MB game, and suddenly—error. "Not enough space." You're standing there scratching your head because, honestly, the math should work, right?
Well, it doesn't.
The question of how many MB is a GB seems like it should have one easy answer. It doesn't. Depending on who you ask—your computer, a hard drive manufacturer, or a math teacher—you’re going to get two very different numbers. It’s either 1,000 or 1,024. And that little "24" makes a massive difference when you start talking about terabytes of data or high-speed fiber internet.
The Short Answer (And Why It’s Complicated)
If you just want the quick-and-dirty version: 1 GB is usually 1,024 MB. That is the binary answer. It’s how your Windows PC thinks. It’s how RAM is built. But if you’re looking at the back of a physical hard drive box or a marketing flyer for a 5G data plan, they almost certainly mean 1 GB is 1,000 MB. Why the split?
It’s basically a turf war between "Base 10" and "Base 2." Humans love Base 10. We have ten fingers. We like round numbers. For us, "kilo" means 1,000. Think kilometers or kilograms. But computers are weird. They don't have fingers; they have transistors that are either "on" or "off." That’s binary—Base 2.
In the binary world, everything is a power of two. $2^{10}$ happens to be 1,024. Early computer scientists saw that 1,024 was "close enough" to 1,000, so they just started calling it a kilobyte. As storage grew, that little rounding error started snowballing. By the time we hit gigabytes, that "close enough" gap became a canyon.
How many MB is a GB in the real world?
Let’s look at how this actually hits your wallet and your devices.
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When you buy a "500 GB" SSD from a brand like Samsung or Western Digital, they are using the Decimal System (SI).
- 1 Kilobyte = 1,000 Bytes
- 1 Megabyte = 1,000,000 Bytes
- 1 Gigabyte = 1,000,000,000 Bytes
Then you plug it into your Windows machine. Windows uses the Binary System. It takes those 500 billion bytes and starts dividing by 1,024.
$500,000,000,000 / 1,024 / 1,024 / 1,024 = 465.66$
Suddenly, your 500 GB drive shows up as 465 GB in File Explorer. You didn't get ripped off, and the drive isn't broken. It's just a translation error. It's like measuring a room in meters and then being surprised when the number is different in yards. Same physical space, different ruler.
The RAM Exception
RAM (Random Access Memory) is the one place where everyone actually agrees. Because of how memory chips are physically wired in rows and columns of binary addresses, you can't really make a "decimal" 8 GB stick of RAM. It has to be binary. So, when you buy 16 GB of RAM, you are genuinely getting $16 \times 1,024 = 16,384$ MB.
What about macOS and iPhone?
Apple actually got tired of people complaining about "missing" storage space. Since macOS Snow Leopard (way back in 2009) and on modern iPhones, Apple switched their operating systems to use decimal. If you buy a 128 GB iPhone, and you use 10 GB of space, the phone says you have 118 GB left. They use the 1,000 MB = 1 GB rule to match the box. It’s arguably more "honest" for consumers, even if hardcore programmers think it’s cheating.
The Secret Language of MiB and GiB
Because of all this legal drama—and yes, hard drive companies have actually been sued over this—the International Electrotechnical Commission (IEC) tried to fix it in 1998. They invented new words.
- Megabyte (MB): 1,000,000 bytes (Decimal)
- Mebibyte (MiB): 1,048,576 bytes (Binary)
- Gigabyte (GB): 1,000,000,000 bytes (Decimal)
- Gibibyte (GiB): 1,073,741,824 bytes (Binary)
Hardly anyone uses these in casual conversation. If you told your friend your video file was 2 "Gibibytes," they’d probably think you were having a stroke. But you'll see these terms in technical specs, Linux distributions, and deep within system monitor tools. If you see "GiB," you know for a fact it's the 1,024 multiplier.
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Real-World Examples: What fits in a GB?
Forget the math for a second. What does a gigabyte actually look like in 2026?
A single gigabyte (1,024 MB) is roughly:
- 300 to 400 high-res photos. If you’re shooting on a modern smartphone with a 48MP or 50MP sensor, those files are huge. You’ll eat through a GB faster than you think.
- 250 songs. Assuming standard compression. If you’re a lossless audio snob (FLAC or ALAC), you might only get 20 or 30 songs.
- 1 hour of standard HD video. If you're watching Netflix in 1080p, expect to burn about 1.5 GB to 3 GB per hour.
- 4K Video? Forget it. A single hour of 4K footage can easily be 20 GB or more.
Why network speeds are even more confusing
Just when you think you’ve got the 1,000 vs 1,024 thing down, the internet providers enter the room.
Internet speed is measured in bits, not bytes. There are 8 bits in a single byte.
So, if you have a "100 Mbps" (Megabits per second) connection, you are not downloading 100 MB of files every second. You have to divide by 8.
$100 / 8 = 12.5$
Your 100 Mbps fiber line actually tops out at 12.5 MB/s. This is the #1 reason people think their internet is slow. They see a 1 GB file and think it should take 10 seconds on a 100 Mbps line. In reality, it takes closer to 80 seconds.
Actionable Takeaways for Managing Your Data
Don't let the math give you a headache. Here is how to actually use this info:
- The 7% Rule: When buying a Windows-based PC or an external hard drive, assume you will "lose" about 7% of the advertised space immediately due to the binary conversion. A 1 TB drive ($1,000$ GB) will give you about 931 GB of usable space.
- Check your cloud limits: Google Drive and iCloud usually count in decimal (1,000 MB). If you are moving files from a Windows PC, the file might look "smaller" on your computer than it does once it hits the cloud.
- Video is the space-killer: If you're running low on space, don't bother deleting emails or Word docs. One minute of 4K video at 60fps is roughly 400 MB. Deleting three minutes of bad footage frees up more space than thousands of text files.
- Formatting matters: Sometimes a "1 GB" file won't fit on a drive because of the "File System overhead." Systems like NTFS or APFS take a small "tax" of storage just to keep track of where the files are.
Understanding how many MB is a GB basically comes down to knowing who is talking. If it’s a salesperson, it’s 1,000. If it’s your computer's operating system, it’s almost certainly 1,024. Next time you see that "disk full" error, you'll know exactly why that "extra" 24 MB matters.