GB to TB Converter
Quick answer: a drive labelled 1 TB holds 1,000 GB by the manufacturer's count, but Windows will show it as roughly 931 GB because the OS counts differently. Type your GB total above to see how it stacks up against drive labels before you buy.
Last updated: May 2026
Type your GB figure above to see the TB equivalent for drive planning.
How to convert gigabytes to terabytes
Large libraries, backups and drive purchases are easier to judge in terabytes, while many file managers and app dashboards still report gigabytes. For planning purposes, 1 GB equals 0.001 TB exactly, the same value written at a different scale.
The formula is terabytes = gigabytes ÷ 1000. In practice, this is useful when deciding whether a new SSD, NAS volume or backup target is large enough for the total amount of data you expect to store.
Typical use cases
- Comparing media libraries with drive capacity
- Planning backups for photos, games, video or project archives
- Checking how much room is left before a storage upgrade is needed
A common use case is a home NAS or media server. People often think in terabytes for buying storage, but the software may display gigabytes.
Quick reference
| GB | TB |
|---|---|
| 100 | 0.1 |
| 1 | 0.001 |
| 500 | 0.5 |
| 1000 | 1 |
| 2000 | 2 |
Related tools
Decimal TB (drive makers) vs binary TiB (what Windows shows)
Drive manufacturers define 1 TB as exactly 1,000,000,000,000 bytes (decimal). Windows counts the same bytes using binary gibibytes (1 GiB = 1,073,741,824 bytes), then labels the result GB. The gap is about 7.4%: a "1 TB" drive shows as 931 GB in Windows. macOS switched to decimal labelling in OS X 10.6 Snow Leopard, so the same drive shows as 1 TB there. Linux distributions have largely adopted correct GiB labels.
This means the same drive can appear to hold different amounts depending on which OS or tool you use, even though the byte count is identical. When planning storage, decide which convention you are working in and stay consistent throughout.
Real-world content sizing
| Content type | Typical size | Per 1 TB (decimal) |
|---|---|---|
| JPEG photo (12 MP, compressed) | 3-5 MB | 200,000-333,000 photos |
| RAW photo (24 MP) | 25-45 MB | 22,000-40,000 photos |
| 1080p video (H.264, 10 Mbps) | ~4.5 GB/hour | ~220 hours |
| 4K video (H.265, 25 Mbps) | ~11 GB/hour | ~90 hours |
| 4K RAW / ProRes (100 Mbps) | ~45 GB/hour | ~22 hours |
| Modern AAA game | 50-150 GB | 7-20 games |
These are estimates; actual sizes depend on codec settings, scene complexity and camera model. Always reserve at least 10-15% of a drive's capacity free: drives slow noticeably and fragment faster when nearly full.
GB to TB: label size versus usable size
When you are shopping for a hard drive or SSD, the GB and TB numbers on the box come from two different counting systems. Here is the sequence of surprises that catches most buyers:
- Drive marketing uses decimal. A "1 TB" drive contains exactly 1,000,000,000,000 bytes. Divide by 1,000 three times and you get 1 TB on the label.
- Windows counts in binary. It divides those same bytes by 1,073,741,824 (1 GiB) per "GB" and lands at 931. So the drive appears as 931 GB in File Explorer, not 1,000 GB. No bytes are missing; the ruler changed.
- macOS switched to decimal in 2009. A Mac shows the same drive as 1.0 TB, matching the box. If you switch from Mac to Windows, drives do not shrink; the display just changed units.
- Formatting takes a further bite. After creating a file system (NTFS, APFS, exFAT), the partition table and reserved sectors consume roughly 1 to 2 percent of raw capacity. A formatted 1 TB drive typically offers about 915 to 925 GB of writable space in Windows.
- Two drives can look equal on the shelf but differ at the OS. A 500 GB SATA SSD and a "500 GB" NVMe may each show as 465 GB in Windows for the same reason: same binary ruler, same result.
The safest approach when planning storage: use the Windows (binary) figure as your working number, add 10 to 15 percent headroom for the file system and drive slowdown near full capacity, then check the box label to confirm the purchase size.
Frequently Asked Questions
I bought a 2 TB drive but Windows only shows 1.81 TB. Where did the rest go?
Nothing is missing. Drive makers count 2 TB as 2,000,000,000,000 bytes (decimal). Windows divides those bytes using binary units (1 GB = 1,073,741,824 bytes) and lands at about 1.81 TB. The 190 GB gap is purely a labelling difference between decimal marketing and binary OS reporting, not lost storage. To check: multiply the Windows figure by 1.0737 and you get back to the manufacturer's byte count.
My NAS shows 931 GB free on a brand-new 1 TB drive. Is the drive faulty?
No. A NAS running Linux typically uses binary GiB labels, so 1,000,000,000,000 bytes shows as 931 GiB (displayed as 931 GB). This is accurate and expected. The drive is healthy; the reporting unit is just binary rather than the decimal TB on the box. You can verify the raw byte count in the NAS admin panel under disk health or S.M.A.R.T. status.
Why does a Mac show 1.0 TB but Windows shows 931 GB for the same drive?
Apple switched to decimal storage reporting in OS X 10.6 Snow Leopard (2009). A Mac divides the raw byte count by 1,000,000,000,000 and labels it TB, matching the box. Windows uses binary division (1,073,741,824 bytes per GB), so the same byte count looks smaller. Neither reading is wrong; they use different unit definitions. When you copy a file between the two systems, every byte transfers correctly.
I need 900 GB for a project backup. Will a 1 TB drive actually fit it?
Probably, but only just. The formatted capacity of a 1 TB drive under Windows is typically 915 to 925 GB after the file system reserves its overhead. A 900 GB backup would fit with 15 to 25 GB to spare. That margin is thin: drives slow noticeably above 90 to 95 percent full, and backup software sometimes needs temporary working space during verification. A 2 TB drive would give you comfortable room and faster sustained writes when the drive is only half full.
Is there a simple rule for converting drive label TB to what Windows will show in GB?
Multiply the label TB by 931 and you get the approximate Windows GB figure. So a 4 TB drive shows as about 3,725 GB (3.63 TB) in File Explorer. The multiplier comes from dividing 1,000,000,000,000 by 1,073,741,824: the ratio of a decimal terabyte to a binary gibibyte. The formula in words: Windows gigabytes equals label terabytes multiplied by 1000, then divided by 1.0737.