Megabytes to Gigabytes: The Complete Guide
Megabytes (MB) and gigabytes (GB) are the most commonly used units for digital storage — photos, videos, apps, and drive capacity. Converting between them is something everyone needs, but the distinction between decimal (SI) and binary (IEC) prefixes causes genuine confusion.
The Conversion Formula
There are two valid answers depending on which standard you're using:
Decimal (SI): GB = MB ÷ 1,000
Binary (IEC): GiB = MiB ÷ 1,024Hard drive manufacturers use decimal (1 GB = 1,000 MB). Operating systems traditionally use binary (Windows shows GB but means GiB). This is why a "1 TB" drive shows as ~931 GB in Windows.
File Size Reference (Decimal)
- 1 MB = 0.001 GB
- 100 MB = 0.1 GB
- 500 MB = 0.5 GB
- 1,000 MB = 1 GB
- 4,000 MB = 4 GB (typical 4K video per hour)
Typical File Sizes for Context
- High-quality JPEG photo: 3–8 MB
- MP3 song (320 kbps, 4 min): ~10 MB
- HD video (1080p, 1 hour): 3–8 GB
- 4K video (1 hour, compressed): 15–45 GB
- Typical smartphone app: 50–500 MB
Why Your Drive Appears Smaller Than Advertised
A 500 GB hard drive = 500,000 MB (decimal). Windows shows this as 500,000 ÷ 1,024 ÷ 1,024 ≈ 476.8 GB (binary GiB). The drive is not defective — the manufacturer and OS are using different definitions.
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