Convert between bits, bytes, kilobytes, megabytes, gigabytes and terabytes in both decimal (1,000) and binary (1,024) units, and estimate download time.
Decimal versus binary units
There are two ways to count data, which is why a "1 TB" drive shows up as about 931 GB on some computers:
- Decimal (SI) units: 1 KB = 1,000 bytes, 1 MB = 1,000,000 bytes, 1 GB = 1,000,000,000 bytes. Used by drive makers and network speeds.
- Binary (IEC) units: 1 KiB = 1,024 bytes, 1 MiB = 1,048,576 bytes, 1 GiB = 1,073,741,824 bytes. Used by many operating systems, though often still labeled "KB", "MB" or "GB".
Bits and bytes
One byte is 8 bits. Internet speeds are measured in bits per second (Mbps), while file sizes are in bytes, so divide the speed by 8 to get megabytes per second. A 100 Mbps connection downloads at most about 12.5 MB per second.
Worked example
1.5 GB is 1,500 MB in decimal units, or about 1,430.5 MiB in binary units. At 100 Mbps, downloading it takes at least 1.5 × 8,000 ÷ 100 = 120 seconds (2 minutes). Real downloads are often slower because of network overhead and server speed.
How much is a gigabyte?
- About 250 to 500 smartphone photos, depending on quality
- About 200 to 250 MP3 songs
- About 1 hour of HD video streaming, depending on the service
Frequently asked questions
Why is my new drive smaller than advertised?
The maker counts 1 TB as 1,000,000,000,000 bytes. Your computer may divide by 1,024 repeatedly and show about 931 "GB" (really GiB). Nothing is missing.
Is MB the same as Mb?
No. MB is megabytes; Mb is megabits. 1 MB = 8 Mb.
Related tools
Results are estimates for planning and education only. They are not financial, tax, legal or medical advice. Check important numbers with a qualified professional.