Data Storage Converter — Why Your 1TB Drive Shows 931GB & How to Convert
Learn why your 1TB drive shows 931GB, the difference between decimal and binary storage units, how network speeds relate to file transfer speeds, and how to convert any data size with a free storage converter.
By sadiqbd · June 9, 2026
Why your new 1TB hard drive shows 931GB — and why it's not a mistake
This is one of the most persistent sources of confusion in computing, and it stems from a straightforward but infuriating discrepancy: hardware manufacturers define storage in base-10 (decimal), while operating systems measure it in base-2 (binary). They use the same words — gigabyte, terabyte — to mean different things, and neither party is technically wrong.
Understanding this distinction, and being able to convert between the units, makes the confusion disappear permanently.
The Two Definitions of Storage Units
Decimal (manufacturer's definition)
- 1 Kilobyte (KB) = 1,000 bytes
- 1 Megabyte (MB) = 1,000 KB = 1,000,000 bytes
- 1 Gigabyte (GB) = 1,000 MB = 1,000,000,000 bytes
- 1 Terabyte (TB) = 1,000 GB = 1,000,000,000,000 bytes
Binary (operating system's definition)
- 1 Kibibyte (KiB) = 1,024 bytes
- 1 Mebibyte (MiB) = 1,024 KiB = 1,048,576 bytes
- 1 Gibibyte (GiB) = 1,024 MiB = 1,073,741,824 bytes
- 1 Tebibyte (TiB) = 1,024 GiB = 1,099,511,627,776 bytes
Windows, macOS, and Linux display storage in binary units but label them GB/TB (instead of the technically correct GiB/TiB). This is the source of the discrepancy.
The "missing" storage explained
A 1TB drive = 1,000,000,000,000 bytes (manufacturer definition)
Your OS divides by 1,073,741,824 (bytes per GiB): 1,000,000,000,000 ÷ 1,073,741,824 = 931.32
The OS displays this as "931 GB" — not because storage is missing, but because it's measuring in GiB while calling it GB. Every byte on the drive is there; you're just looking at the same count through a different lens.
How to Use the Data Storage Converter on sadiqbd.com
- Enter the value — the storage amount you want to convert
- Select the source unit — bytes, KB, MB, GB, TB (decimal) or KiB, MiB, GiB, TiB (binary)
- Read the converted value — in your target unit
Real-World Scenarios
Planning cloud storage
You have 22,000 photos averaging 5.5MB each and need to pick a cloud storage plan.
22,000 × 5.5MB = 121,000MB = 121 GB (decimal)
In actual OS-displayed storage (converting to GiB): 121,000MB ÷ 1,024 ÷ 1,024 = 115.4 GiB (displayed as ~115 GB on your device)
A 128GB cloud plan should work. A 100GB plan won't.
Understanding network speed vs. file transfer speed
Your ISP advertises 200 Mbps (megabits per second). You're downloading a 4GB file. How long?
Convert speed: 200 Mbps ÷ 8 bits/byte = 25 MB/s (megabytes per second) Convert file size: 4 GB = 4,000 MB Time = 4,000 ÷ 25 = 160 seconds (about 2.7 minutes) under ideal conditions
In practice, speeds vary — this is a theoretical minimum. But the calculation shows why a "200 Mbps" connection doesn't mean 200 MB/s file downloads.
Sizing a backup drive
You need to back up:
- 90,000 photos at 6MB average = 540,000MB = 540GB
- 2TB of video files
- 200GB of documents and other files
Total: 540GB + 2,000GB + 200GB = 2,740GB = 2.74TB (decimal)
Buy a 3TB or 4TB drive for comfortable headroom. After OS formatting overhead (filesystem structures use ~1–3% of capacity), the actual available space on a 3TB drive is approximately 2.7–2.75TB.
Server provisioning
You're provisioning a virtual machine needing 512GiB of RAM (as shown by the cloud provider). What is that in GB (decimal)?
512 GiB × 1,073,741,824 bytes/GiB = 549,755,813,888 bytes ÷ 1,000,000,000 = 549.76 GB
Cloud providers typically charge by GiB but display in GB — confirming which unit is being billed matters for cost forecasting.
The Bits vs. Bytes Trap
The two most confused units:
- Bit (b, lowercase): 0 or 1 — the smallest unit of digital information
- Byte (B, uppercase): 8 bits
Network speeds are almost always in bits per second (Mbps, Gbps). File sizes are almost always in bytes (MB, GB, TB).
Converting: divide bits by 8 to get bytes.
100 Mbps internet = 100 ÷ 8 = 12.5 MB/s download speed
This is why your browser's download progress shows a fraction of your advertised speed in MB/s — the ISP quotes in megabits, the browser reports in megabytes.
Storage Unit Reference Card
| What you see on device | What manufacturer advertised | Actual bytes |
|---|---|---|
| 128 GB (≈119 GiB) | 128 GB | 128,000,000,000 |
| 256 GB (≈238 GiB) | 256 GB | 256,000,000,000 |
| 512 GB (≈476 GiB) | 512 GB | 512,000,000,000 |
| 1 TB (≈931 GiB) | 1 TB | 1,000,000,000,000 |
| 2 TB (≈1.82 TiB) | 2 TB | 2,000,000,000,000 |
Frequently Asked Questions
Is there any storage "missing" from my drive? No — every byte that was manufactured is there. The discrepancy is purely a units definition difference. Decimal TB (manufacturer) vs. binary TiB (OS) gives different numbers for the same physical bytes.
Does SSD storage show the same discrepancy as HDD? Yes — the same decimal/binary definition difference applies regardless of storage technology.
Why don't OS makers just use decimal like manufacturers? Binary units are more natural for computers because memory and address spaces are powers of 2. Binary GiB aligns perfectly with memory architecture. Decimal GB is practical for marketing. Both have legitimate technical justifications.
Is the data storage converter free? Yes — completely free, no sign-up required.
Once you understand the decimal/binary unit distinction, the "missing storage" mystery is solved permanently. The converter makes the numbers work out correctly regardless of which system any given spec sheet uses.
Try the Data Storage Converter free at sadiqbd.com — convert between bits, bytes, KB, MB, GB, TB, and their binary equivalents instantly.
