Download Time

Calculate how long will it take to download a file over various Internet connection speeds. Enter the size of the file and select the file size units from the drop-down box. The download time is calculated automatically.

Check also the free Online File Size calculator and converter.


What is Download Time?

Download time is the time needed to transfer a file from the Internet to a local machine or device. This time is determined by the connection speed and the size of the file.

Protocol overhead

Calculating the download time by dividing the size of the file by the connection speed may not be exact in a real-world scenario. This is because there are many factors that influence this process and reduce the speed. For example, the most common TCP/IP protocol transfers the data in packets which include some internal data that is needed for its operation. Such data is about 5% of the total data transferred.

For TCP over IPv4 over Ethernet you have (without header options):

The L3 maximum packet size of 1500 results in a total L1 data size of 1500+18+20 = 1538 bytes and a maximum L4 payload size of 1500-20-20 = 1460 bytes.

Lost packet

There is also the "packet-loss" factor which may further reduce the transfer speed. As the information travels through many devices and over a very long distance some packets may get lost due to various reasons - bad cables, defective hardware, overloaded devices, etc. In such case, the lost packet is sent again from the server from where a file is downloaded which further reduces the bandwidth and increases the download time. In a properly working connection, such value is close to zero.

Server bandwidth

The download speed is determined not only by the connection speed of the downloading party but also the connection speed of the server that sends the data. If the server has slower connection speed than the receiving party then the maximum transfer speed is limited to one of the servers. Of course, in practice servers send data to multiple users simultaneously which may further reduce the transfer speed.