Data Transfer Rate Converter
The Reason Your 100 Mbps Connection Downloads at 12 MB/s
Nothing is broken. Internet service providers sell bandwidth in bits per second; download managers report progress in bytes per second. There are eight bits in a byte, so the number your browser shows will always be roughly an eighth of the number on the bill. A 100 Mbps line delivers 12.5 MB/s at full rate — that is the connection working exactly as sold. This converter makes the factor-of-eight translation explicit in both directions.
The Formula
Every unit is stored as its value in bits per second, and conversion pivots through that base:
(Factors are relative to 1 bit/second)
The byte units simply carry a factor eight times their bit counterparts: a kilobit/second is 1000, a kilobyte/second is 8000. Negative rates are rejected.
Decimal Prefixes, Not Binary
This converter uses SI decimal prefixes throughout — kilo means 1000, mega means 1,000,000, giga means 1,000,000,000. That matches how network equipment and ISPs actually specify throughput. It is deliberately not the binary convention (1024-based) that operating systems sometimes use for file sizes, which is the second reason reported speeds and advertised speeds can appear to disagree.
| Unit | Code | Bits/Second |
|---|---|---|
| Bits/Second | bps | 1 |
| Kilobits/Second | kbps | 1,000 |
| Megabits/Second | mbps | 1,000,000 |
| Gigabits/Second | gbps | 1,000,000,000 |
| Terabits/Second | tbps | 1,000,000,000,000 |
| Bytes/Second | Bps | 8 |
| Kilobytes/Second | KBps | 8,000 |
| Megabytes/Second | MBps | 8,000,000 |
| Gigabytes/Second | GBps | 8,000,000,000 |
b is a bit; an uppercase B is a byte. Mbps and MBps differ by a factor of eight, and the distinction is the single most common source of confusion in this subject.Advertised Speed to Real Download Rate
What each common connection tier delivers at its theoretical maximum:
| Connection (Mbps) | MB/s | KB/s |
|---|---|---|
| 1 | 0.125 | 125 |
| 10 | 1.25 | 1250 |
| 25 | 3.125 | 3125 |
| 50 | 6.25 | 6250 |
| 100 | 12.5 | 12500 |
| 300 | 37.5 | 37500 |
| 500 | 62.5 | 62500 |
| 1000 (1 Gbps) | 125 | 125000 |
These are line rates. Real-world throughput is lower once protocol overhead, contention and server-side limits are accounted for — the conversion gives you the ceiling, not a guarantee.
The Eight-to-One Relationship
The bar lengths are to scale: the byte figure is one eighth of the bit figure.
Full Cross-Reference
| 1 of… | bit/s | Mbit/s | MB/s | GB/s |
|---|---|---|---|---|
| Bit/Second | 1 | 0.000001 | 1.25e-07 | 1.25e-10 |
| Kilobit/Second | 1000 | 0.001 | 0.000125 | 1.25e-07 |
| Megabit/Second | 1000000 | 1 | 0.125 | 0.000125 |
| Gigabit/Second | 1000000000 | 1000 | 125 | 0.125 |
| Terabit/Second | 1.0e+12 | 1000000 | 125000 | 125 |
| Byte/Second | 8 | 0.000008 | 0.000001 | 1.0e-09 |
| Kilobyte/Second | 8000 | 0.008 | 0.001 | 0.000001 |
| Megabyte/Second | 8000000 | 8 | 1 | 0.001 |
| Gigabyte/Second | 8000000000 | 8000 | 1000 | 1 |
Where This Conversion Earns Its Keep
- Checking you're getting what you pay for — a speed test reporting MB/s has to be multiplied by eight before it can be compared with an advertised Mbps tier.
- Capacity planning — sizing an uplink for a known number of concurrent streams, where stream bitrates are quoted in Mbps and storage throughput in MB/s.
- Backup windows — working out whether a given dataset can traverse a link overnight requires the link rate and the data size in compatible units.
- Storage versus network bottleneck analysis — drive throughput is specified in MB/s, network throughput in Gbps; converting both to one unit reveals which is the constraint.
How to Use This Calculator
- Enter the rate figure in the Value field.
- In the first dropdown pick the unit it's given in — read the case carefully, since Mbps and MBps are both listed.
- In the second dropdown pick your target unit.
- Press Calculate. The explanation shows both factors in bits per second and the division performed.
Related Calculations
For the power draw of the equipment moving that data, see the Power Conversion Calculator; for its energy consumption over time, the Energy Conversion Calculator.