Mbps against MB/s, with download times calculated
Connection speeds are quoted in megabits per second and file sizes in megabytes, and a byte is 8 bits, so divide. A 100 Mbps line moves 12.5 MB/s at best, which is 1 min 20 s for a 1 GB file and 1 h 7 min for a 50 GB one. A 1 Gbps line moves 125 MB/s and takes 8 s for that same 1 GB file.
Line speed against transfer rate and download time
The megabits column is the advertised line speed, the only source figure in the table. Megabytes per second is that divided by 8, the number of bits in a byte, as defined in IEC 80000-13. The download times are calculated from it for files of 1, 10, 50 decimal gigabytes, at the full line rate with no overhead, so treat every one of them as a floor rather than a forecast.
| Line speed | Megabits per second | Megabytes per second | 1 GB file | 10 GB file | 50 GB file |
|---|---|---|---|---|---|
| 10 Mbps | 10 | 1.25 | 13 min 20 s | 2 h 13 min | 11 h 7 min |
| 25 Mbps | 25 | 3.13 | 5 min 20 s | 53 min 20 s | 4 h 27 min |
| 50 Mbps | 50 | 6.25 | 2 min 40 s | 26 min 40 s | 2 h 13 min |
| 100 Mbps | 100 | 12.5 | 1 min 20 s | 13 min 20 s | 1 h 7 min |
| 200 Mbps | 200 | 25 | 40 s | 6 min 40 s | 33 min 20 s |
| 300 Mbps | 300 | 37.5 | 27 s | 4 min 27 s | 22 min 13 s |
| 500 Mbps | 500 | 62.5 | 16 s | 2 min 40 s | 13 min 20 s |
| 1 Gbps | 1,000 | 125 | 8 s | 1 min 20 s | 6 min 40 s |
| 2.5 Gbps | 2,500 | 312.5 | 3 s | 32 s | 2 min 40 s |
| 10 Gbps | 10,000 | 1,250 | 1 s | 8 s | 40 s |
Reuse this data
Published under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence. Copy it, adapt it, republish it, commercial use included, as long as you credit UnitGlide, https://unitglide.net and link back to this page. No permission request and no fee.
Copy this
<iframe src="https://unitglide.net/embed/reference/data-rate-and-download-time"
width="100%" height="520" loading="lazy"
style="border:1px solid #e2e6ec;border-radius:12px"
title="Mbps against MB/s, with download times calculated"></iframe>
<p><a href="https://unitglide.net/reference/data-rate-and-download-time">Mbps against MB/s, with download times calculated</a> by UnitGlide, CC BY 4.0</p>Result
The frame is served from this site, so it keeps the attribution link attached and picks up any correction automatically. If you would rather hold the numbers yourself, the whole table is on this page under the same licence.
One letter, a factor of eight
Mb is a megabit and MB is a megabyte, and there are 8 bits in a byte. Internet connections are sold in bits per second, file sizes and download managers report bytes, and mistaking one for the other is not a rounding error but an eightfold one. It is by far the largest unit mistake on this site.
The conversion is a single division. 100 Mbps is 12.5 MB/s, 1,000 Mbps is 125 MB/s, and any speed you are quoted divides the same way. If a download manager reports roughly an eighth of the number on your bill, nothing is wrong.
IEC 80000-13 is the standard that fixes the symbols: bit for the bit, B for the byte, and the binary prefixes that go with them. It is the same standard that gives the kibibyte its name, which is the other trap in the same family and has its own reference table here.
Why this matters: these times are floors, not forecasts
Every download time in the table is the arithmetic minimum at the full advertised rate. Real transfers lose a few percent to protocol overhead before anything else happens, because TCP/IP headers travel over the same line as the payload, and the difference between 1 min 20 s and what you observe starts there.
After that come the causes that dominate in practice: the server's own upload capacity, the path between it and you, congestion at peak hours, Wi-Fi rather than cable, and an older router that cannot forward at line rate. On a fast connection the bottleneck is very rarely the connection.
This is why the 2,500 and 10,000 Mbps rows matter less than they look. Multiplying your line speed by ten does not divide a real download by ten unless every other link in the chain also scales, and single-stream transfers usually stop scaling long before that.
Decimal gigabytes, and where the other error hides
The file sizes here are decimal gigabytes: 1 GB is 1,000,000,000 bytes. That is the convention for file sizes and for the storage a drive is sold with. Software that divides by 1,024 will call the same file 0.93 GB while meaning gibibytes, which is a 7.37 percent difference on top of everything else.
The two errors stack in a nasty way. A file listed as 1 GiB moved over a link quoted in megabits is two conversions away from an honest estimate, and the factor of 8 and the factor of 1.073742 pull in the same direction rather than cancelling.
If you need a quick mental figure, divide megabits by ten rather than by eight. The extra twenty percent absorbs protocol overhead and leaves you with an estimate that is usually closer to what you will actually see than the exact arithmetic in the table.
Frequently asked questions
How many MB/s is 100 Mbps?
12.5 MB/s, because a byte is 8 bits and 100 divided by 8 is 12.5. That is the theoretical maximum at the full line rate; protocol overhead and the server at the other end usually put real transfers a few percent below it.
How long does it take to download a 50 GB game?
1 h 7 min on a 100 Mbps connection at full rate, 6 min 40 s on a 1 Gbps connection, and 4 h 27 min on 25 Mbps. Game downloads also decompress and install as they go, so the wall-clock time is often longer than the transfer time.
Why is my download speed only a tenth of my internet speed?
Because your plan is quoted in megabits and your download manager reports megabytes, a factor of 8, plus a few percent of protocol overhead. A 100 Mbps line showing about 12.5 MB/s is performing exactly as advertised.
Is 1 Gbps the same as 1000 Mbps?
Yes. Network speeds use decimal prefixes, so 1 Gbps is exactly 1,000 Mbps, or 125 MB/s. Unlike storage capacity, data rates have never been quoted in powers of 1,024, so no binary interpretation applies here.
Does upgrading from 500 Mbps to 1 Gbps halve my download times?
Only if nothing else is the bottleneck. In arithmetic, a 10 GB file goes from 2 min 40 s to 1 min 20 s. In practice the server's upload capacity, the route, your Wi-Fi and your router all sit in the path, and on a connection this fast one of them is usually slower than the line.
Can I republish this table?
Yes, under Creative Commons Attribution 4.0 International (CC BY 4.0). Credit UnitGlide, https://unitglide.net and link back, and you may copy, adapt and republish it, commercial use included. The embed keeps the credit attached and picks up any correction automatically.
Sources
- IEC 80000-13, Quantities and units, Part 13: Information science and technology, for the bit and the byte, the symbols bit and B, and the eight bits that make one byte.
- NIST: Prefixes for binary multiples, for the decimal and binary prefixes that separate the gigabyte from the gibibyte.
- BIPM, SI Brochure, for the decimal SI prefixes that network speeds in Mbps and Gbps are quoted with.