Download Time Calculator
Enter a file size and your internet speed to see how long the download takes. Or work out the speed you need, or how much you can download in a set time.
Rough example sizes to start from; edit the number to match your file. GB counts in 1000s, GiB in 1024s (what Windows shows as “GB”).
Plans are sold in megabits (Mbps, small b). Apps often show megabytes (MB/s, big B): 1 MB/s = 8 Mbps.
0% gives the best-case time. About 10% is a common rule of thumb for protocol overhead; Wi-Fi and busy servers can take more.
Many plans upload much slower than they download. Add yours to see the upload time.
The number of files multiplies the size above; the extra boxes add other files on top.
Typical ballpark bitrates; each service and setting differs. GB per hour = Mbps × 0.45.
Time for this size at common speeds
| Speed | MB each second | Best case | With 10% overhead |
|---|
How your download time is worked out
Turn the size into bits, take off any overhead, divide by the speed, then tidy up the seconds.
- 1
Size into bits
5 GB × 8,000
= 40,000 Mbit - 2
Speed that's left
100 Mbps × 100%
= 100 Mbps - 3
Bits ÷ speed
40,000 ÷ 100
= 400 s - 4
Into h, min and s
400 s
= 6 min 40 s
Read more: the formula, a worked example, bits vs bytes and decimal vs binary
A download is a race between the size of the file and the speed of your line. The catch is that the two are measured in different units: files in bytes and internet speeds in bits per second. Turn the size into bits first, then divide.
The formula
size in bits = size in bytes × 8
speed that's left = speed × (1 − overhead ÷ 100)
download time (s) = size in bits ÷ speed that's left
speed needed = size in bits ÷ time ÷ (1 − overhead ÷ 100)
size you can get = speed that's left × time ÷ 8
streaming GB per hour = bitrate in Mbps × 3,600 ÷ 8 ÷ 1,000 = Mbps × 0.45
Worked example
A 5 GB file on a 100 Mbps line. 1 GB is 1,000,000,000 bytes, or 8,000 megabits, so 5 GB is 5 × 8,000 = 40,000 Mbit. With no overhead the speed that's left is 100 × 1 = 100 Mbps. Time = 40,000 ÷ 100 = 400 s, which is 6 × 60 = 360 s plus 40 s: 6 min 40 s.
With 10% overhead the speed that's left is 100 × 0.9 = 90 Mbps, so the time is 40,000 ÷ 90 = 444.4 s, or 7 min 24 s. The line moves 100 ÷ 8 = 12.5 MB each second at best, or 11.25 MB with the overhead.
The other way round: to get the same 5 GB in 6 min 40 s (400 s) you need 40,000 ÷ 400 = 100 Mbps. And in 400 s a 100 Mbps line can bring in 100 × 400 ÷ 8 = 5,000 MB = 5 GB.
Bits and bytes
A bit is a single 0 or 1; a byte is 8 bits. Storage is in bytes (big B: MB, GB) and internet plans in bits per second (small b: Mbps, Gbps). So divide Mbps by 8 for MB/s: 100 Mbps = 12.5 MB/s, 1 Gbps = 125 MB/s. Steam, game consoles and browsers often show MB/s, which is why the number looks smaller than your plan.
Decimal and binary sizes
Decimal units count in 1000s: 1 kB = 1,000 bytes, 1 MB = 1,000 kB, 1 GB = 1,000 MB. Binary units count in 1024s: 1 KiB = 1,024 bytes, 1 MiB = 1,024 KiB, 1 GiB = 1,024 MiB = 1,073,741,824 bytes. Windows uses 1024s but still writes “GB”, so a 5 GB file shows there as 5,000,000,000 ÷ 1,073,741,824 = 4.66 “GB”. Internet speeds always use 1000s.
| Unit | Bytes | Megabits |
|---|---|---|
| 1 MB | 1,000,000 | 8 |
| 1 MiB | 1,048,576 | 8.389 |
| 1 GB | 1,000,000,000 | 8,000 |
| 1 GiB | 1,073,741,824 | 8,589.93 |
| 1 TB | 1,000,000,000,000 | 8,000,000 |
| 1 TiB | 1,099,511,627,776 | 8,796,093 |
Why real downloads are slower
Every packet carries some address and checking data (TCP/IP headers), Wi-Fi loses some speed to the radio link, and the server you download from may be the slowest part. Others in your home share the line too. Allowing about 10% is a common rule of thumb; on weak Wi-Fi or a busy server it can be 25% or more. Run a speed test and use that number for a closer answer.
Upload vs download
The sum is the same both ways, only the speed changes. Cable and DSL plans often upload 10 to 20 times slower than they download, so a cloud backup of 64 GB at 20 Mbps takes 64 × 8,000 ÷ 20 = 25,600 s, about 7 h 7 min, while the download at 100 Mbps takes 1 h 25 min. Fibre plans are often the same speed both ways.
Streaming data
Streaming is a download that runs as you watch. Data per hour = bitrate × 3,600 seconds ÷ 8 bits per byte. At 5 Mbps that is 5 × 3,600 ÷ 8 = 2,250 MB = 2.25 GB an hour; 2 hours a day for 30 days is 2.25 × 2 × 30 = 135 GB a month. Typical ballpark bitrates are about 1 Mbps for SD, 5 Mbps for HD and 15–25 Mbps for 4K, but every service and setting is different.
Example sizes and bitrates are rough starting points, not figures for any specific product. Units follow IEC 80000-13. Checked 13 October 2026.
Common questions
How long does it take to download 1 GB?
1 GB is 8,000 megabits. At 100 Mbps that is 8,000 ÷ 100 = 80 seconds; at 50 Mbps 160 seconds (2 min 40 s); at 1 Gbps 8 seconds. Those are best-case times at the full speed; real downloads are often a little slower.
Why is my download slower than my internet speed?
Internet speeds are sold in megabits per second (Mbps), but file sizes are in megabytes (MB). One byte is 8 bits, so a 100 Mbps line moves at most 12.5 MB each second. On top of that, protocol overhead, Wi-Fi, a busy server or other people on the line all cut the speed. Allowing about 10% for overhead is a common rule of thumb.
What is the difference between Mbps and MB/s?
Mbps is megabits per second; MB/s is megabytes per second. Divide Mbps by 8 to get MB/s: 100 Mbps = 12.5 MB/s, 1 Gbps = 125 MB/s. Download apps and game stores often show MB/s, while internet plans are sold in Mbps.
What speed do I need to download a game in an hour?
Turn the size into bits and divide by 3,600 seconds. A 100 GB game is 800,000 megabits, so you need 800,000 ÷ 3,600 = 222 Mbps, or about 247 Mbps if you allow 10% overhead. Pick “Speed needed” above to work it out for any size and time.
Is upload time the same as download time?
The sum is the same, but the speed often isn’t. Many cable and DSL plans upload far slower than they download, for example 500 Mbps down and 20 Mbps up, so backing up a phone to the cloud can take much longer than downloading the same amount. Fibre plans are often the same speed both ways.
How much data does streaming use per hour?
Multiply the video bitrate in Mbps by 0.45 to get GB per hour. About 5 Mbps (a typical HD stream) uses about 2.25 GB an hour; about 16 Mbps (a typical 4K stream) uses about 7.2 GB an hour. Services change their bitrates, so check your app’s own figure if you need it exactly.
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Made by Zulu Calculator, part of AlphaZulu LLC. Formulas are shown in full and rule figures are checked against official sources; see how we build calculators.