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Download Time Calculator
Enter the size of a file and the speed of your connection to estimate how long a download or upload will take. Units are handled for you, including the bits-versus-bytes difference, and you can allow for real-world overhead.
The formula and the bits-versus-bytes trap
Download time is the amount of data divided by the rate it arrives at. Both must be in the same unit, so the calculator converts the file size to bits and the speed to bits per second.
Time (s) = file size in bytes × 8 ÷ (speed in bits per second × efficiency)
The factor of 8 is where most mistakes come from. Internet plans are advertised in megabits per second (Mbps), but downloads show file sizes and progress in megabytes (MB). A 100 Mbps connection moves at most 12.5 MB per second. A 5 GB file at that rate takes 5,000 MB ÷ 12.5 MB/s = 400 seconds, or 6 minutes 40 seconds.
Watch the capital letters: Mb or Mbps means megabits, MB or MB/s means megabytes.
Decimal and binary size units
Storage makers and network engineers usually use decimal prefixes, where 1 GB is 1,000,000,000 bytes. Operating systems and memory use binary prefixes in some places, where 1 GiB is 1,073,741,824 bytes, about 7.4% larger. The difference grows with size: a 1 TiB file is 10% larger than 1 TB. Choose the unit your file listing actually reports. If a file manager says GB but the number came from software that counts in powers of 1,024, the binary option will match it better.
| Prefix | Decimal | Binary |
|---|---|---|
| Kilo | 1,000 bytes | 1,024 bytes |
| Mega | 10^6 bytes | 2^20 bytes |
| Giga | 10^9 bytes | 2^30 bytes |
Why real downloads are slower
The result is a best case at the efficiency you choose. In practice, network protocols add header overhead, Wi-Fi shares airtime between devices, and the server may limit how fast it will send. Other devices on the same connection reduce your share, and speeds can drop at busy times. Distance and latency matter for some transfers, particularly many small files, which are slower than one large file of the same total size.
To find a realistic efficiency, run a speed test, divide the measured result by the plan speed, and enter that percentage. Uploads are often slower than downloads on home connections, so enter the upload rate when sending files.
Limits
The calculation assumes a steady rate for the entire transfer. Real speeds vary from second to second, and some services slow large downloads after a quota is used. Treat the answer as a planning estimate and add a margin when a deadline depends on it.
For large transfers, consider whether the bottleneck is the network at all. A slow disk, a busy computer or a limit set by the sending service can cap the rate below the link speed, and the efficiency box is the simplest way to model that. Resumable downloads and checksums are also worth using on big files, since a dropped connection near the end otherwise wastes all the time already spent.
Worked example
A 700 MB file is transferred over a link that sustains 5 megabytes per second.
Inputs
| File size | 700 |
|---|---|
| Size unit | Megabytes (MB, 10^6 bytes) |
| Connection speed | 5 |
| Speed unit | Megabytes per second (MB/s) |
| Efficiency | 100 % |
Result
About 140 seconds in total at 5.000 MB/s effective.
| File size in bits | 5,600,000,000 |
|---|---|
| Effective speed | 40.000 Mbps = 5.000 MB/s |
| Time in seconds | 140.0 |
| Time in minutes | 2.33 |
| Time in hours | 0.039 |
The same file at other speeds (at your efficiency setting)
| Speed | Time |
|---|---|
| 1 Mbps | 1 h 33 min 20 s |
| 10 Mbps | 9 min 20 s |
| 50 Mbps | 1 min 52 s |
| 100 Mbps | 56 s |
| 500 Mbps | 11 s |
| 1 Gbps | 6 s |
- Speeds are rated in bits per second, files are sized in bytes, and one byte is eight bits.
Accuracy note: Results are calculated in your browser from the values you enter. Check anything that matters for legal, academic or financial purposes against the official source.
Frequently asked questions
How long does it take to download 1 GB on a 100 Mbps connection?
At the full rated speed, 1 GB is 8,000 megabits, so it takes 80 seconds. Real downloads usually take somewhat longer because of overhead and other traffic.
What is the difference between Mbps and MB/s?
Mbps is megabits per second and MB/s is megabytes per second. One byte is eight bits, so divide a speed in Mbps by 8 to get the maximum download rate in megabytes per second.
Why is my download slower than my plan speed?
Wi-Fi quality, other devices, server limits, protocol overhead and congestion all take a share. Use the efficiency setting to model the fraction of the plan speed you really get.
Should I choose GB or GiB?
Use GB for decimal sizes, as most storage and download pages report, and GiB for binary sizes. The two differ by about 7.4% at the gigabyte level.
Does the calculator work for uploads?
Yes. Enter your upload speed instead of the download speed. Upload rates on many home connections are lower, so the time can be much longer for the same file.