GB vs GiB - what's the difference in disc size?

GB and GiB are defined as:

• Gigabyte (GB) 1000³ = 1,000,000,000 <---- in SI system
• Gibibyte (GiB) 1024³ = 1,073,741,824 <---- in IEC 60027-2

In IT typically GB means 1,073,741,824 (it means, GB is used to describe memory size in IT).

Almost always, manufacturers describe disk size using GB from SI system (1GB = 1000³ bytes).

Practical example:

2_877_227_008 / 1024 / 1024 / 1024 = 2.67962646484375      <---- this one on the screenshot
2_877_227_008 / 1000 / 1000 / 1000 = 2.8772270079999998

so, Microsoft Windows shows GB as 1024 * 104 * 1024

References

1. https://en.wikipedia.org/wiki/Gigabyte