Phones, apps & storage
Download Time Calculator
Enter a file size and a connection speed and this gives you the download time — using the conversion people get wrong (a 100 Mbps line moves 12.5 MB per second, not 100) and an overhead allowance for what real connections deliver against what they advertise.
Megabits are not megabytes
Connection speeds are sold in megabits per second; files are measured in megabytes. There are eight bits in a byte, so a 100 Mbps line moves 12.5 MB per second at best. This single factor-of-eight is behind almost every "why is my fast internet so slow" complaint.
Why you never get the advertised speed
- Protocol overhead. TCP/IP headers, acknowledgements and retransmissions consume 3–8% of raw throughput before anything useful moves.
- Wi-Fi. A device on Wi-Fi commonly sees 50–70% of the line rate, and shares airtime with every other device on the band. Wired is the only way to test what the connection can really do.
- Server limits. Downloads are as fast as the slower end. A CDN edge node under load caps you well below your line speed, and the app store is often that bottleneck.
- Mobile contention. Advertised 5G figures are peak, single-user, close to the mast. Typical real throughput is a fraction of it.
Storage units add a second gap
A "4.5 GB" game listing usually means 4.5 decimal gigabytes, but if your device reports binary gibibytes the same file reads as 4.19 GiB. Both figures are correct; they count differently. The file size converter handles the translation.
Questions people ask about this
How long does it take to download a 4.5GB game on 100 Mbps?
About six minutes at the theoretical maximum, and roughly seven minutes at a realistic 85% efficiency. The arithmetic: 4.5 GB is 4,608 MB, which is 36,864 megabits; divided by 100 Mbps that is 369 seconds, and 434 seconds once overhead is allowed for.
Why is my download slower than my internet speed?
Most often because the speed is in megabits and the file is in megabytes — a factor of eight. After that come Wi-Fi losses, which typically cost 30–50% of the line rate, protocol overhead at 3–8%, and the server at the other end, which frequently caps you below your own connection.
How many megabytes per second is 100 Mbps?
12.5 MB/s at the theoretical maximum, and around 10.6 MB/s in practice once overhead is subtracted. Divide any megabit figure by eight to get megabytes: 25 Mbps is 3.1 MB/s, 300 Mbps is 37.5 MB/s, and a gigabit line moves 125 MB/s.
Where these numbers come from
Rates on this page were last checked against the published price lists on . Grading companies change fees and pause tiers without notice — confirm the total on the submission form before you pay.