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Convert gigabytes to terabytes
Type a number and see it converted as you type. 1 gigabyte = 0.001 terabytes, so the conversion is simply × 0.001.
The formula
terabytes = gigabytes × 0.001
gigabytes to terabytes — quick reference
| gigabytes (GB) | terabytes (TB) |
|---|---|
| 1 | 0.001 |
| 2 | 0.002 |
| 3 | 0.003 |
| 4 | 0.004 |
| 5 | 0.005 |
| 10 | 0.01 |
| 15 | 0.015 |
| 20 | 0.02 |
| 25 | 0.025 |
| 50 | 0.05 |
| 75 | 0.075 |
| 100 | 0.1 |
| 250 | 0.25 |
| 500 | 0.5 |
| 1,000 | 1 |
Backup planning is where gigabytes turn into a drive purchase
A 400 GB photo library, 900 GB of video projects and a 300 GB system image come to 1.6 TB, and the decision that follows is which drive to buy. Sizing to the current total is the standard mistake: a backup target needs headroom for versions and snapshots, which routinely consume half again as much as the source data.
Redundancy takes another cut before anything is stored. Two 4 TB drives mirrored hold 4 TB, not 8, and a filesystem’s own metadata and reserved blocks remove a few per cent more. Converting the requirement into terabytes is the first step; the drive that actually satisfies it is usually one size above the answer.
At terabyte scale the decimal and binary gap reaches ten per cent
This tool works in decimal — 1,000 GB to the terabyte, the definition every manufacturer uses on the box. Windows reports in binary while writing "TB", and the divergence compounds with each prefix: about 2.4% at kilobytes, 4.9% at megabytes, 7.4% at gigabytes and very nearly 10% here.
A single terabyte drive therefore presents as 931 GB rather than 1,000, close to 70 GB of apparent shortfall, and it scales with every drive added to the plan. A total assembled from gigabyte figures that Explorer reported, then divided by 1,000, quietly understates what the hardware must hold. Figures gathered on macOS or Linux are already decimal and match the box.
Questions
How many terabytes are in 1 gigabyte?
1 gigabyte = 0.001 terabytes. To convert any amount, multiply by 0.001.
What is the formula to convert gigabytes to terabytes?
terabytes = gigabytes × 0.001. That is exactly what the calculator above does, so you can check its working.
Is the conversion exact?
It depends on what you mean by "kilo". This tool uses the decimal SI convention (1 KB = 1000 bytes), the one storage manufacturers use. Operating systems often use 1024 instead, which is why a drive reports less space than the box promises.
Updated 2026-07-20. The conversion runs in your browser — nothing is uploaded.