Why does my 1TB hard drive show less than 1TB in Windows?

Manufacturers advertise storage using decimal units (1 TB = 1,000,000,000,000 bytes), while Windows reports it using binary units (1 TiB = 1,099,511,627,776 bytes) but labels it 'TB'. The drive isn't missing space — it's the same bytes measured two different ways, showing about a 10% gap.

How many MB are in a GB?

Using the decimal standard (as manufacturers and most file sizes use), 1 GB = 1,000 MB. Using the binary standard (as some operating systems display), 1 GiB = 1,024 MiB.

What's the difference between GB and GiB?

GB (gigabyte) is the decimal unit equal to 1,000,000,000 bytes. GiB (gibibyte) is the binary unit equal to 1,073,741,824 bytes. They're often used interchangeably in casual speech, but they differ by about 7.4%.

How many bytes are in a kilobyte?

In the decimal standard, 1 KB = 1,000 bytes. In the binary standard used by most operating systems for file sizes, 1 KiB = 1,024 bytes.

How long does it take to download a 5GB file?

It depends on your internet speed, measured in megabits per second (Mbps), not megabytes. A 5GB (40 gigabit) file on a 100 Mbps connection takes roughly 400 seconds (about 6.7 minutes) at full, uninterrupted speed.

Why is my download speed in Mbps but my file size in MB?

Internet speeds are traditionally measured in bits per second (a legacy from telecom networking), while file sizes are measured in bytes. There are 8 bits in a byte, so a 100 Mbps connection downloads at roughly 12.5 MB per second, not 100 MB per second.

Data Size Converter – Bytes, KB, MB, GB & TB (Free, Instant)

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How It Works

Why Your 1TB Drive Shows Less Than 1TB

This is the single most common data-size confusion, and it isn't a scam or a defect — it's two different definitions of the same word.

Decimal Standard (Manufacturers)

1 GB = 1,000 MB = 1,000,000,000 bytes

Used on the box for drives, SSDs, and USB sticks, matching the SI system.

Binary Standard (Operating Systems)

1 GiB = 1,024 MiB = 1,073,741,824 bytes (shown as "GB")

Windows, macOS, and Linux typically label this "GB" even though it's technically a GiB.

Worked Example: A "1TB" Drive in Windows

Manufacturer's 1 TB = 1,000,000,000,000 bytes.

Windows divides that by 1,024³ (1,099,511,627,776) to show its "TB" figure.

✓ 1,000,000,000,000 ÷ 1,099,511,627,776 ≈ 0.909 TB — so Windows shows about 909 GB, roughly a 9% "loss" that's really just a different unit definition.

Quick Reference

Decimal vs. Binary Units Side by Side

Decimal (SI)	Bytes	Binary (IEC)	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	1,000,000,000,000,000	1 PiB	1,125,899,906,842,624

Practical Guide

Comparing Storage Devices & Cloud Plans

Why a 128GB Phone Never Shows 128GB Free

Beyond the decimal/binary gap, the operating system, pre-installed apps, and system partitions also take up real space, so a "128GB" phone typically shows around 110-120GB available even before you add any files.

Comparing Cloud Storage Plans Fairly

Cloud providers (Google Drive, iCloud, Dropbox, OneDrive) generally use decimal GB for their plan sizes, matching manufacturer conventions — so a "100GB" cloud plan and a "100GB" hard drive use the same definition, even if your OS displays them differently.

Photos, Videos & Typical File Sizes

A smartphone photo is typically 3-8 MB, a minute of 1080p video is roughly 60-130 MB, and a two-hour 4K movie can run 15-25 GB — useful benchmarks when estimating how much storage you actually need.

FAQ

Data Size Converter — Frequently Asked Questions

Common questions about storage units, drive capacity, and download times.