TB to GB Converter
Type a number of terabytes and the equivalent in gigabytes appears as you type. Tick the SI box to count 1,000 gigabytes per terabyte instead of 1,024.
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Created by the Reeliy Editorial Team. Last updated: Oct 19, 2026
How many gigabytes are in a terabyte?
There are two correct answers, because the prefix tera is used in two different ways. In the decimal (SI) system a terabyte is 1012 bytes and a gigabyte is 109 bytes, so 1 TB = 1,000 GB. In the binary convention a terabyte is 240 bytes and a gigabyte is 230 bytes, so 1 TB = 1,024 GB.
GB = TB × 1,024Binary count, the converter's default.
GB = TB × 1,000Decimal SI count, used when "Use SI standard" is ticked.
Memory sizes and many operating system tools have traditionally counted in powers of two, while drive makers, network providers, macOS and iOS count in powers of ten. Neither side is wrong; they are answering different questions. The converter starts with the binary count and switches to the decimal one when you tick the box.
To remove the ambiguity, the IEC defined separate names for the binary units: the tebibyte (TiB) is 240 bytes and the gibibyte (GiB) is 230 bytes, so 1 TiB is exactly 1,024 GiB. Everyday speech still uses TB and GB for both.
How to convert TB to GB
- Enter the number of terabytes in the first box. Decimals are fine.
- Decide which count you need. Leave the SI box empty for 1,024 GB per TB, or tick it for 1,000 GB per TB.
- Read the gigabytes in the second box. The answer is rounded to four decimal places, and a box you clear leaves the last answer in place.
Example 1. A 2.5 TB archive is 2.5 × 1,024 = 2,560 GB in binary units, or 2.5 × 1,000 = 2,500 GB in decimal units.
Example 2. A 0.75 TB backup disk holds 0.75 × 1,024 = 768 GB (binary) or 0.75 × 1,000 = 750 GB (decimal).
Example 3. To go the other way, divide: 4,096 GB ÷ 1,024 = 4 TB. The GB to TB converter does that for you.
Why does a 1 TB drive show less than 1 TB?
A drive sold as 1 TB stores 1,000,000,000,000 bytes. A system that reports sizes in binary units divides that by 230 bytes for each "GB" and displays 1012 ÷ 230 ≈ 931.32. No space has vanished: the same number of bytes is simply counted in larger units. A small further amount is used by the file system's own bookkeeping once the drive is formatted.
| Advertised size | Bytes | Shown in binary units |
|---|---|---|
| 0.5 TB | 500,000,000,000 | 465.66 GB |
| 1 TB | 1,000,000,000,000 | 931.32 GB |
| 2 TB | 2,000,000,000,000 | 1,862.65 GB |
| 4 TB | 4,000,000,000,000 | 3,725.29 GB |
| 8 TB | 8,000,000,000,000 | 7,450.58 GB |
| 16 TB | 16,000,000,000,000 | 14,901.16 GB |
The gap grows with each prefix step. A decimal kilobyte is about 2.3% smaller than a binary one, a megabyte 4.6%, a gigabyte 6.9% and a terabyte 9.1%, which is why the mismatch is most visible on large drives.
How big are a TB and a GB?
A gigabyte is a comfortable unit for single files: a short HD video, an operating system update or a game patch. A terabyte is the unit for collections: a laptop's whole disk, a backup set, or a year of high-resolution footage.
For scale, assume an average phone photo of 4 MB and an HD film of 4 GB. A decimal terabyte then holds about 250,000 photos (1012 ÷ 4,000,000) or about 250 films (1,000 GB ÷ 4 GB). Real files vary a lot, so treat these as rough planning figures.
TB to GB conversion table
| Terabytes (TB) | Gigabytes, binary (× 1,024) | Gigabytes, SI (× 1,000) |
|---|---|---|
| 0.25 | 256 | 250 |
| 0.5 | 512 | 500 |
| 1 | 1,024 | 1,000 |
| 2 | 2,048 | 2,000 |
| 3 | 3,072 | 3,000 |
| 4 | 4,096 | 4,000 |
| 5 | 5,120 | 5,000 |
| 8 | 8,192 | 8,000 |
| 10 | 10,240 | 10,000 |
| 12 | 12,288 | 12,000 |
| 16 | 16,384 | 16,000 |
| 20 | 20,480 | 20,000 |
| 100 | 102,400 | 100,000 |
Common mistakes
- Mixing bits and bytes. A capital B means bytes and a lowercase b means bits, so 1 Tb is only 0.125 TB. The bits to bytes converter covers the factor of eight.
- Comparing a label with an operating system. Compare like with like: a drive's decimal label against a decimal count, or the system's binary figure against a binary count.
- Assuming one convention everywhere. Cloud storage plans and download sizes are usually decimal, while RAM is always binary.
Frequently asked questions
How many GB are in 1 TB?
1,000 GB by the decimal SI definition and 1,024 GB by the binary one. The converter shows 1,024 by default and 1,000 when "Use SI standard" is ticked.
Should I use 1,000 or 1,024?
Use 1,000 when you are matching a drive label, a cloud storage plan or a network quota. Use 1,024 when you are matching what Windows or a memory specification reports. When in doubt about a purchase, the 1,000 figure is what the seller counts.
Why does my 1 TB drive show about 931 GB?
The drive holds 1012 bytes. A system that counts in binary units divides by 230 per gigabyte and reports about 931.32, so the capacity is the same and only the unit changes.
How do I convert GB to TB?
Divide by 1,024 for the binary count or by 1,000 for the decimal count. For example 2,048 GB is 2 TB in binary and 2.048 TB in decimal. The GB to TB converter does it automatically.
References
- NIST, Prefixes for binary multiples
- BIPM, The International System of Units (SI Brochure)
- IEC 80000-13, Quantities and units: Information science and technology
Cite this converter and page
If you use this page in your work, you can cite it as:
Reeliy Editorial Team. (2026). TB to GB Converter. Reeliy. https://reeliy.com/converters/convert-tb-to-gb“TB to GB Converter.” Reeliy, 2026, https://reeliy.com/converters/convert-tb-to-gb.