What is meant by Gigabyte, Megabyte, GB and MB?
Many customers stumble over the terms GB and MB – and sometimes you also see GiB or MiB. This article explains these units in a simple way, highlights common pitfalls, and helps you understand how operating systems, storage devices, and internet providers display data sizes.
Quick Summary (TL;DR)
- Byte is the basic unit of data size. 1 Byte = 8 Bits.
- There are two systems of measurement:
- Decimal (SI): 1 kB = 1,000 Bytes, 1 MB = 1,000,000 Bytes, 1 GB = 1,000,000,000 Bytes.
- Binary (IEC): 1 KiB = 1,024 Bytes, 1 MiB = 1,048,576 Bytes, 1 GiB = 1,073,741,824 Bytes.
- Manufacturers of hard drives/SSDs usually use decimal (GB/MB), while many operating systems calculate internally in binary (GiB/MiB) – that’s why displayed values often differ.
- Network/Internet is almost always measured in bits per second (Mbit/s or Gbps). When downloading files you often see MB/s. Conversion rule: 8 Mbit/s ≈ 1 MB/s.
Basic Concepts: Bit & Byte
- Bit (b): the smallest information unit, 0 or 1.
- Byte (B): 8 Bits – the standard unit for file sizes.
Important: The B in MB/GB stands for Byte, while the b in Mbit/Gbit stands for bit. Case sensitivity changes the meaning!
Two Systems: Decimal (SI) vs. Binary (IEC)
Decimal (SI)
- Used by measurement standards and storage manufacturers.
- 1 kB = 1,000 B, 1 MB = 1,000,000 B, 1 GB = 1,000,000,000 B.
Binary (IEC)
- Reflects the way computers work (binary system).
- Introduced clear naming: KiB, MiB, GiB.
- 1 KiB = 1,024 B, 1 MiB = 1,048,576 B, 1 GiB = 1,073,741,824 B.
Why are there differences?
A “1 TB” storage device (decimal) has 1,000,000,000,000 Bytes. An operating system that uses binary calculation will show this as ≈ 931 GiB. Both values are correct – they just use different systems.
Conversion Table (compact)
| Unit | Decimal (SI) | Binary (IEC) |
|---|---|---|
| 1 kB / 1 KiB | 1,000 B | 1,024 B |
| 1 MB / 1 MiB | 1,000,000 B | 1,048,576 B |
| 1 GB / 1 GiB | 1,000,000,000 B | 1,073,741,824 B |
| 1 TB / 1 TiB | 1,000,000,000,000 B | 1,099,511,627,776 B |
Rules of thumb:
1 GiB ≈ 1.074 GB (or 1 GB ≈ 0.931 GiB).
From Mbit/s to MB/s: divide by 8.
Practical Example: “Why does my computer show fewer GB?”
You buy an SSD with 500 GB (decimal). That equals 500,000,000,000 Bytes. In binary this is ≈ 465.66 GiB. Many systems then display ≈ 465 GB (actually GiB, but often labeled incorrectly). Additionally, file systems and partition tables reserve some space – so the usable capacity is slightly smaller.
Network: MB/s vs. Mbit/s
Internet providers usually advertise with Mbit/s (e.g. 100 Mbit/s). Browsers and download tools often display MB/s.
Calculation: 100 Mbit/s ÷ 8 = 12.5 MB/s (theoretical). In reality, protocol overhead, latency, and server limits reduce the rate – around 10–11 MB/s is typical.
Typical File Sizes (approximate)
- 1 photo (smartphone, JPEG/HEIC): 2–6 MB
- 1 song (MP3, 320 kbit/s): 6–12 MB
- 1 hour Full-HD video (H.264): 1–3 GB
- 1 hour 4K video (H.265): 7–15 GB
- 1 email without attachment: a few KB
In Web Hosting
- Webspace/storage is usually given in GB – mostly decimal.
- Traffic/Bandwidth per month may be shown in GB/TB (data volume) or in Mbit/s (throughput).
- Email mailboxes: Quotas are often set in MB or GB. Many small attachments add up quickly.
- Backups: Compression reduces size, but large media libraries remain large.
Common Pitfalls & Tips
- Mind capitalization: MB ≠ Mb.
- Marketing vs. display: Packaging (decimal) vs. OS display (binary).
- Compare tools: Different programs round differently. For exact values: check in Bytes.
- Measure performance correctly: Read/write speed in MB/s ≠ network speed in Mbit/s.
- Plan for file system overhead: Some space is always reserved for system data.
FAQ
Is “GB” always the same as “GiB”?
No. GB = decimal, GiB = binary. Many systems display GiB but label it as “GB”.
Why does my Mac/Windows show different values than my NAS?
macOS displays decimal (GB), while many NAS systems and Windows tools display binary (GiB).
How large can an email be?
Often around 25 MB. Due to encoding, attachments grow internally by ~33%. Better: send large files via link.
How should I plan webspace?
Add up your media files, backups, and database sizes, then add 20–30% buffer.
Related Articles
- Understanding Disk Usage in cPanel
- Bandwidth vs. Traffic: What’s the Difference?
- Backup Strategies for Websites
- Image Optimization for the Web
- Email Limits and Large Attachments
- SSD vs. HDD in Hosting
Conclusion
The units MB and GB are not complicated – the key is knowing which system (decimal vs. binary) is being used and whether we are talking about bits or Bytes. With this knowledge you can interpret manufacturer specifications, operating system displays, and hosting plans correctly and plan more effectively.
