Why is my new drive smaller than advertised?

Nothing is missing. Manufacturers count in decimal units and Windows displays binary units under decimal labels, which loses about 7 percent at gigabyte scale and 10 percent at terabyte scale. macOS has reported decimal since 2009, which is why the same drive shows a larger number there.

What is the difference between Mbps and MBps?

Mbps is megabits per second and MBps is megabytes per second. There are 8 bits in a byte, so a 100 Mbps connection tops out at about 12.5 MB per second in a download manager. Internet plans are advertised in bits, file transfers are usually reported in bytes.

How much data does streaming actually use?

Roughly 1 GB per hour for standard definition, 3 GB per hour for 1080p, and 7 GB per hour for 4K, though modern codecs on newer services reduce this. Music streaming at high quality uses about 150 MB per hour.

Should I use KiB and MiB in my own work?

In technical documentation, yes, because they remove all ambiguity. In consumer-facing text, most readers expect KB and MB, so state the base you are using once and stay consistent.

Bytes ↔ KB/MB/GB/TB

Convert between data storage units

Value

From

Quick Facts

•1 KB = 1,024 bytes
•1 GB = 1,073,741,824 bytes
•1 TB = 1,024 GB

Understanding Data Storage Units

Digital storage uses a binary system: 1 KB = 1,024 bytes, 1 MB = 1,024 KB, 1 GB = 1,024 MB, and 1 TB = 1,024 GB. However, storage manufacturers often use decimal (1 KB = 1,000 bytes), which is why a '1 TB' drive shows less capacity in your OS.

Practical Reference

A typical photo is 3–5 MB, an HD movie is 4–5 GB, and a smartphone today has 128–512 GB of storage. Understanding these units helps you estimate storage needs and internet data usage.

Understanding the bytes ↔ kb/mb/gb/tb

Storage confusion comes from two different meanings of the same prefix. Drive manufacturers use decimal units where a gigabyte is a billion bytes, while operating systems traditionally report binary units where a gibibyte is 1,073,741,824 bytes. That is why a 1 TB drive shows as 931 GB.

Worked examples

Why a 1 TB drive shows 931 GB

1The manufacturer sells 1,000,000,000,000 bytes.
2Windows divides by 1024 three times: 1,000,000,000,000 ÷ 1024³ = 931.32.
3It then labels the result GB even though the unit is technically GiB.

1 decimal TB equals 931.32 GiB, so no storage is missing.

How long a 25 GB download takes on 100 Mbps

1Convert the file to bits: 25 GB × 8 = 200 gigabits, which is 200,000 megabits.
2Divide by the line rate: 200,000 ÷ 100 = 2,000 seconds.
3That is 33.3 minutes at the full theoretical rate.
4Real throughput is typically 80 to 90 percent, so allow 37 to 42 minutes.

About 35 to 40 minutes for a 25 GB download on a 100 Mbps connection.

Decimal versus binary units

Decimal unit	Bytes	Binary unit	Bytes
1 kB	1,000	1 KiB	1,024
1 MB	1,000,000	1 MiB	1,048,576
1 GB	1,000,000,000	1 GiB	1,073,741,824
1 TB	1,000,000,000,000	1 TiB	1,099,511,627,776
1 PB	10^15	1 PiB	1,125,899,906,842,624

The gap widens with each step: 2.4 percent at kilo, 4.9 percent at mega, 7.4 percent at giga, and 10 percent at tera.

Typical file sizes

Content	Approximate size
Text document	20 to 100 KB
Phone photo (12 MP JPEG)	3 to 5 MB
RAW photo	25 to 45 MB
Three minute MP3 at 320 kbps	7 MB
One hour of 1080p streaming	3 GB
One hour of 4K streaming	7 GB
One minute of 4K phone video	350 MB
Modern AAA game	80 to 150 GB

Frequently asked questions

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Understanding Data Storage Units: Bytes to Terabytes

Demystify data storage units and understand why your 1TB drive doesn't actually show 1TB of available space.

This calculator is for educational and reference purposes only. Always verify critical calculations independently.