File Download Time Calculator (GB over Mbps Connection Speed)
A 100 Mbps connection does not download 100 MB per second. Megabits are one eighth of a megabyte, so the theoretical ceiling is 12.5 MB per second, and TCP overhead, Wi-Fi contention and server-side throttling typically shave another ten to thirty-five percent off that in real conditions.
Internet speeds are quoted in megabits, file sizes in megabytes — the factor of eight is the single most common source of confusion.
| Connection | Speed | Effective | Transfer time |
|---|---|---|---|
| ADSL | 10 Mbps | 8.5 Mbps | 13h 23m 8s |
| Basic fibre | 50 Mbps | 42.5 Mbps | 2h 40m 38s |
| Standard fibre | 100 Mbps | 85.0 Mbps | 1h 20m 19s |
| Fast fibre | 300 Mbps | 255.0 Mbps | 26m 46s |
| Gigabit | 1000 Mbps | 850.0 Mbps | 8m 2s |
| 5G mobile | 200 Mbps | 170.0 Mbps | 40m 9s |
Bits, bytes and the factor of eight
Internet service providers advertise in megabits per second (Mbps, lowercase b); operating systems display transfer rates in megabytes per second (MB/s, uppercase B). Divide the advertised figure by eight to get the best-case download rate: 100 Mbps is 12.5 MB/s, 1 Gbps is 125 MB/s.
Where the missing bandwidth goes
Protocol overhead from TCP, IP and TLS headers consumes roughly three to five percent. Wi-Fi adds contention and retransmission losses of ten to fifteen percent on 5 GHz and considerably more on congested 2.4 GHz. Single-stream downloads are also frequently capped by the source server rather than by your line.
Upload is usually the bottleneck
Most residential connections are asymmetric: a 500/50 package uploads at one tenth of its download rate. Backing up a 200 GB video project on 50 Mbps upload takes about nine hours at best. Symmetric fibre or scheduled overnight transfers are the practical fixes.
Download time by file size and speed
| File size | 10 Mbps | 50 Mbps | 100 Mbps | 500 Mbps | 1 Gbps |
|---|---|---|---|---|---|
| 1 GB | 13m 40s | 2m 44s | 1m 22s | 16s | 8s |
| 5 GB | 1h 8m | 13m 40s | 6m 50s | 1m 22s | 41s |
| 20 GB | 4h 33m | 54m 40s | 27m 20s | 5m 28s | 2m 44s |
| 50 GB | 11h 23m | 2h 17m | 1h 8m | 13m 40s | 6m 50s |
| 100 GB | 22h 45m | 4h 33m | 2h 17m | 27m 20s | 13m 40s |
| 1 TB | 9d 12h | 1d 22h | 23h 17m | 4h 39m | 2h 20s |
At 100% theoretical efficiency; expect ten to thirty-five percent longer in practice.
People also ask
How long does it take to download 50GB on 100 Mbps?
About one hour and eight minutes at the theoretical maximum, and closer to one hour and twenty minutes over good Wi-Fi once overhead is included.
Why is my download slower than my advertised speed?
Protocol overhead, Wi-Fi losses, network congestion, and server-side limits. Wired ethernet on an uncongested line typically delivers ninety percent or more of the advertised rate.
Is Mbps the same as MB/s?
No. Divide Mbps by eight to get MB/s. A 200 Mbps line peaks at 25 MB/s.
Three worked examples
Same engine, three different starting points — useful if you want to see how sensitive the answer is before you type your own numbers in.
Example 1: file size 39, size unit "MB"
On the lower / more conservative end. Internet speeds are quoted in megabits, file sizes in megabytes — the factor of eight is the single most common source of confusion.
Example 2: file size 50, size unit "GB"
A typical middle-of-the-road setup. Internet speeds are quoted in megabits, file sizes in megabytes — the factor of eight is the single most common source of confusion.
Example 3: file size 65, size unit "TB"
On the higher / more demanding end. Internet speeds are quoted in megabits, file sizes in megabytes — the factor of eight is the single most common source of confusion.
Quick answers about the Download / Upload Time
What exactly does the Download / Upload Time work out?
A 100 Mbps connection does not download 100 MB per second. You enter file size, size unit, connection speed and real-world efficiency and the result panel updates straight away, so you can compare two or three versions of the same question in a few seconds.
What do I need before I start?
Only 4 fields: file size, size unit, connection speed and real-world efficiency. Nothing else is needed and nothing is stored.
How is it calculated — bits, bytes and the factor of eight?
Internet service providers advertise in megabits per second (Mbps, lowercase b); operating systems display transfer rates in megabytes per second (MB/s, uppercase B). The same maths runs inside this page, so hand-checking the result on paper gives you the identical figure.
Why do two calculators give me different answers for download / Upload Time?
Protocol overhead from TCP, IP and TLS headers consumes roughly three to five percent. Different sites pick different assumptions, so always check which method a calculator states before you trust the gap between two numbers.
What does the "Download time by file size and speed" table on this page tell me?
It is the reference range this tool works against — 6 rows from "1 GB" (13m 40s) up to "1 TB" (9d 12h). Use it to sanity-check whether the number you just calculated sits where you expected it to. At 100% theoretical efficiency; expect ten to thirty-five percent longer in practice.
Which size unit should I pick?
The dropdown offers 3 choices — MB, GB and TB. Pick the one that matches your real situation rather than the one you would like to be true; size unit usually moves the final figure more than any other single input, so it is worth running it twice with the option above and below your guess.
Does it work in both metric and imperial (or another currency)?
Yes. The "Size unit" control converts every field and every result, so you never have to convert anything by hand before typing it in. Switch it after entering your numbers and the output re-renders instantly in the new system.
Do I have to press a button or reload the page to see the result?
No. Download / Upload Time runs completely inside your browser, so the moment you change a value the cards recalculate — there is no submit step, no page reload and no waiting for a server round trip. That also means it keeps working on a weak or intermittent mobile connection.
Is it free, and do you keep what I type?
It is free with no sign-up, no app install and no usage limit. Nothing you enter into Download / Upload Time leaves your device — the calculation is JavaScript running locally, so there is no upload of your figures to DrHint or anyone else.
Can I use it on a phone?
Yes — the layout stacks to a single column on small screens and the number fields open the numeric keypad on both Android and iOS. Many people bookmark this page or add it to their home screen and re-open it whenever the question comes up.
Anything to be careful about with the result?
About one hour and eight minutes at the theoretical maximum, and closer to one hour and twenty minutes over good Wi-Fi once overhead is included. Treat the output as a well-grounded estimate for planning, not as a professional, legal or medical decision on its own.
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