Start with bits and bytes
A bit is a binary digit. A byte is a group of eight bits. Their symbols are case-sensitive: b means bit and B means byte. That small typographic difference matters because 100 megabits per second (100 Mb/s) equals 12.5 megabytes per second (12.5 MB/s) before protocol overhead.
Storage capacity and file size are usually stated in bytes, while network connection rates are commonly stated in bits per second. Always convert bits to bytes—or bytes to bits—before comparing a connection rate with a file size.
Decimal and binary prefixes are different
SI prefixes are powers of ten: kilo means 1,000, mega means 1,000,000, and giga means 1,000,000,000. IEC binary prefixes name powers of 1,024: kibi, mebi, and gibi. Using their distinct symbols keeps the quantity unambiguous.
- 1 kB = 1,000 B; 1 KiB = 1,024 B.
- 1 MB = 1,000,000 B; 1 MiB = 1,048,576 B.
- 1 GB = 1,000,000,000 B; 1 GiB = 1,073,741,824 B.
- 1 TB = 1,000,000,000,000 B; 1 TiB = 1,099,511,627,776 B.
Why a drive can appear smaller
Drive makers normally advertise decimal capacity. A 1 TB drive therefore contains 1,000,000,000,000 bytes before formatting and system use. That same byte count is about 931.323 GiB. If an interface reports the binary quantity but labels it ‘GB,’ the displayed number looks lower even though the underlying capacity has not disappeared.
Formatting, recovery partitions, file-system metadata, and reserved system space can reduce usable space further. Separate that real overhead from the unit-label difference when diagnosing capacity.
Compare storage and speeds correctly
Preserve the exact symbol from each product or interface. Convert both values to bytes for capacity or bits per second for transfer rate, then compare. ConvertPulse’s MB, GB, and TB tools use decimal units, matching their SI-style symbols and most advertised storage values.
A transfer-time estimate also needs consistent units. A decimal 5 GB file contains 40 Gb. On an ideal 100 Mb/s link, dividing 40,000 Mb by 100 Mb/s gives 400 seconds. Real transfers take longer because of protocol overhead, congestion, storage speed, and other system limits.
- Do not use MB and MiB—or GB and GiB—as synonyms.
- Check capitalization: MB/s is eight times Mb/s.
- State whether a result uses decimal or binary prefixes.
- Treat advertised link speed as a ceiling, not a guaranteed file-transfer rate.
Put this guide into practice
These tools deliberately use decimal storage units; use the labels above when comparing their results with a binary GiB or TiB display.
- Megabytes to gigabytes: Convert decimal MB to decimal GB.
- Gigabytes to megabytes: Reverse the decimal capacity conversion.
- Gigabytes to terabytes: Scale advertised storage capacity to decimal TB.
- Terabytes to gigabytes: Convert decimal TB back to decimal GB.
Sources and standards
The definitions and factors in this guide were checked against these primary standards and government references.