The exact equivalent
A gigabyte is 1,000,000,000 bytes and a gibibyte is 1,073,741,824. So 1 GB is 0.9313 GiB, a gap of about 7% that grows with each prefix step.
1 GB = 0.93132257 GiB
1 GiB = 1.07374182 GB
How to convert it by hand
Just multiply by the conversion factor. To go from gigabytes to gibibytes, multiply by 0.931323; to come back, divide by that same number or multiply by 1.073742.
For example: 25 GB × 0.931323 = 23.2831 GiB.
A tip that saves mistakes: check the result goes the way you expect. If gibibytes are a smaller unit than gigabytes, the number has to come out bigger. If it comes out smaller, you divided when you should have multiplied.
Conversion table
| GB | GiB |
|---|---|
| 1 | 0.9313 |
| 2 | 1.8626 |
| 5 | 4.6566 |
| 10 | 9.3132 |
| 20 | 18.6265 |
| 50 | 46.5661 |
| 100 | 93.1323 |
Reference points to picture it
| Reference | Equals |
|---|---|
| A 1 TB drive | 931 GiB shown by the system |
| 1 GB | 0.931 GiB |
| 1 GiB | 1.074 GB |
| A 500 GB SSD | 465.7 GiB |
The trick for doing it in your head
Take off 7% going from GB to GiB, and add 7.4% going the other way. At terabyte scale the gap is closer to 9%.
It is fine for getting by without a phone, but not for anything that depends on precision: in a recipe, on a building site or in a dose, use the exact conversion.