Bytes to Bits Converter
Convert bytes to bits by multiplying by 8. Includes a data-size table, the difference between MB and Mb in internet speeds, and why decimal and binary prefixes disagree.
Bytes to bits
Formula
Multiply by 8.
A byte is eight bits — that has been settled since the 1960s, though early machines used 6-, 7- and 9-bit bytes, which is why formal standards prefer the unambiguous term octet.
Worked example
A 25 MB file on a 100 Mbps connection. The file is in megabytes, the line speed in megabits, so convert first:
Forgetting the factor of 8 is why a "100 Mb" connection seems to download at only 12.5 MB/s — it is doing exactly what it promised.
Conversion table
| Bytes (B) | Bits (b) |
|---|---|
| 1 | 8 |
| 2 | 16 |
| 8 | 64 |
| 16 | 128 |
| 64 | 512 |
| 100 | 800 |
| 512 | 4,096 |
| 1,000 | 8,000 |
| 1,024 | 8,192 |
| 10,000 | 80,000 |
| 1,000,000 | 8,000,000 |
MB versus Mb
The capital letter carries the whole meaning, and it is the source of endless confusion:
- MB — megabyte. Used for file sizes and storage. A photo is 4 MB.
- Mb — megabit. Used for transfer rates. A connection is 100 Mb/s.
To turn a line speed into a realistic download rate, divide the megabits by 8: 100 Mb/s is at best 12.5 MB/s. Protocol overhead takes a few percent more on top of that.
Decimal and binary prefixes
There are two incompatible meanings of "kilo" in computing, and they drift further apart as the units grow:
- Decimal (SI) — 1 kB = 1,000 bytes, 1 MB = 10⁶, 1 GB = 10⁹. Used by drive manufacturers, network equipment and macOS.
- Binary (IEC) — 1 KiB = 1,024 bytes, 1 MiB = 2²⁰, 1 GiB = 2³⁰. Used by Windows, RAM sizing and most programming tools.
The gap is 2.4% at kilo, 7.4% at giga and 10% at tera. That is why a "1 TB" drive shows as 931 GB in Windows: the drive holds 10¹² bytes, and Windows divides by 2⁴⁰ while still writing "GB".
FAQ
How many bits is 1 byte? 8 bits.
How many bytes is 1 bit? 0.125 bytes — a bit is the smaller unit, so a byte cannot be subdivided into whole bytes.
Why is a byte 8 bits? Eight bits hold 256 values, enough for a character set plus control codes, and it is a power of two, which makes addressing hardware simple. IBM's System/360 settled it as the industry norm.
Is a nibble a real unit? Yes — four bits, or half a byte. It maps to exactly one hexadecimal digit.
How do I convert a download speed to a file-transfer time? Convert the file to bits, then divide by the line speed in bits per second. A 25 MB file is 200 Mb, so it needs 2 seconds at 100 Mb/s.