IPTools.

Change and remember theme. Choosing light or dark saves your preference in this browser. “System” removes it and follows your device settings.

Planning

Download time and bandwidth calculator

Calculate download time, bandwidth or file size. Compare Mbps with MB/s, GB with GiB, and account for transfer efficiency.

Prepared by: IPTools — editorial methodPublished: Updated: Report an issue
New to this tool? Start here.

Click an example below the form. Look at the result, then change one value to compare what happens.

Bits and bytes
One byte (B) is 8 bits (b). Files are usually measured in bytes, while link speed is measured in bits per second, such as Mbps.
GB / GiB
1 GB is one billion bytes; 1 GiB is 1,073,741,824 bytes. The same number with a different unit means a different size.
Efficiency
How much of the stated speed carries your data. 100% gives the theoretical minimum time. A lower value allows for assumed overhead; it is not a speed test.

01 / Input

Start with your data

Local
Greater than 0 and at most 100.
Try an example

Your data is processed in the browser. Sharing a result is your choice.

02 / Your result

A result you can understand.

Fill in the form or choose an example. You will see the values and how they were calculated.

How to use it

Choose the unknown value and enter the other two. MB and GB are decimal; MiB and GiB are binary. Efficiency accounts for assumed overhead; the result is an estimate.

A little network lab

Why does 100 Mbps not mean 100 MB/s?

You want to transfer a 1 GB file over a 100 Mbps link. Match the units before dividing size by speed.

Example result1 GB / 100 Mbps → 80 secondsOpen example in calculator

  1. 1 GB is 1,000,000,000 bytes. Each byte has 8 bits, so the file contains 8,000,000,000 bits.

  2. 100 Mbps is 100,000,000 bits per second. Dividing 8,000,000,000 by 100,000,000 gives 80 seconds.

  3. At an assumed efficiency of 80%, useful data travels at 80 Mbps. Time rises to 100 seconds. This is a model assumption, not a link measurement.

Your turn

How long does 2 GB at 100 Mbps take in theory?

Show answer and explanation

160 seconds at 100% efficiency, or 200 seconds at 80%. Doubling the file size at the same speed doubles the time.

Official documents

Standards & sources

Sources checked:

The date refers to checking the listed documents and registries, not endorsement by their authors. Calculation assumptions and limits appear with the result. How we prepare the material.