Download Time Calculator
How long a download takes at a given speed.
File sizes are in bytes; connection speeds are in bits per second. There are 8 bits in a byte, so a 100 Mbps link transfers about 12.5 MB per second.
How to use
- 1 Enter the file size and choose its unit (KB, MB, GB, TB).
- 2 Enter your connection speed and choose its unit (Kbps, Mbps, Gbps).
- 3 Read the estimated download time in seconds and as a duration.
- 4 Copy the figure if you need it.
About Download Time Calculator
The Download Time Calculator estimates how long a file will take to transfer over a connection of a given speed.
Enter the file size, pick its unit, enter your connection speed and its unit, and it returns the time both as a plain number of seconds and as a friendly human-readable duration like "1m 20s" or "2h 14m".
The reason people get this wrong is the difference between bits and bytes.
File sizes are measured in bytes (KB, MB, GB, TB), but connection speeds are quoted in bits per second (Kbps, Mbps, Gbps), and there are eight bits in a byte.
That single factor of eight is why a "100 Mbps" line does not download a 100 MB file in one second — it moves about 12.5 megabytes per second, so the file takes around eight seconds.
This tool routes every calculation through bits explicitly, so the conversion is always correct no matter which units you mix.
It is handy for sanity-checking whether a large download or upload will finish before you need to leave, comparing broadband packages, or estimating how long backing up a folder will take.
The calculation is a pure client-side function — nothing is uploaded, nothing is tracked — and it works offline.
Real-world transfers are usually a little slower than the theoretical figure because of overhead and congestion, so treat the result as a best case.
FAQ
Why is the download slower than my advertised speed?
Speeds are quoted in bits per second while files are measured in bytes, and there are 8 bits per byte. Real transfers are also slowed by protocol overhead and network congestion.
What is the difference between Mbps and MB/s?
Mbps is megabits per second; MB/s is megabytes per second. Divide a Mbps figure by 8 to get the approximate MB/s, so 100 Mbps is about 12.5 MB/s.
Is the estimate exact?
It is a theoretical best case from size and speed alone. Actual time is usually a bit longer due to overhead, so treat it as a lower bound.