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Download Time Calculator

Estimate how long a file will take to download or upload at a given connection speed, allowing for real-world overhead.

Your numbers

%

Real transfers rarely reach the full advertised speed. 10% is a reasonable start.

Realistic download time

7m 24s

At full advertised speed
6m 40s
Effective speed
11.25 MB/s
Seconds at full speed
400.0
The math behind it

  1. At full speed

    5 GB × 8 bits ÷ 100 Mbpsequals6m 40s

  2. Allowing 10% overhead

    6m 40s ÷ (1 − 10%)equals7m 24s

Internet speeds are quoted in bits per second, but file sizes are shown in bytes. There are 8 bits in a byte, which is why a 100 Mbps connection downloads at about 12.5 megabytes per second, not 100. This calculator handles the conversion and adds an allowance for the overhead every real connection has.

How it works

Convert the file size to bits by multiplying by 8, then divide by the connection speed in bits per second. That gives the time at the full advertised speed.

Real transfers are slower. Network protocols add their own data, Wi-Fi loses some speed, and the server at the other end may be the bottleneck. The overhead allowance reduces the speed by that percentage to give a more realistic estimate.

Sizes here use decimal units (1 GB = 1,000,000,000 bytes), the same way network speeds and most download pages are measured.

A worked example

A 5 GB file on a 100 Mbps connection is 40,000,000,000 bits. At the full 100 Mbps that takes 400 seconds, or 6m 40s. With a 10% overhead allowance it takes about 7m 24s, at an effective 11.25 MB/s.

Questions people ask

Why is my download slower than my internet plan?

Plans advertise the maximum speed to your home. Wi-Fi, other devices on the network, busy times of day and the speed of the server you are downloading from can all lower what you actually get.

Does this work for uploads?

Yes. Enter your upload speed instead. On many home connections the upload speed is much lower than the download speed, so large uploads take noticeably longer.

What is the difference between Mbps and MB/s?

Mbps is megabits per second and MB/s is megabytes per second. Divide Mbps by 8 to get MB/s. Download managers usually show MB/s, while internet plans are sold in Mbps.

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