Bandwidth Calculator

The bandwidth calculator answers common questions that come up when transferring data over a network. It combines four functions: conversions between data amounts, calculation of the time required to download or upload files, estimation of the bandwidth needed by a website based on its traffic and conversion of monthly hosting allotment volume into sustained speed.

By selecting a mode above the corresponding fields will be adjusted. The tools for download time and hosting allow bi-directional calculations. Enter the values you want to calculate and the tool will derive the other values from it.

What is bandwidth?

In computer science, bandwidth refers to the speed of data transfer and is measured in bits per second. It's usually expressed in metric multiples such as kilobits, megabits, and gigabits, abbreviated as kbps, mbps, and gbps respectively.

The bandwidth quoted is a maximum and not guaranteed. There may be differences between the advertised speed and what you can actually achieve due to protocol overhead, encryption, congestion and server load. So lines advertised at a certain bit rate per second will usually be slightly slower when transferring files in practice.

The ratio between bits and bytes is eight.

This is often the most confusing part. A byte consists of 8 bits. The connection speed is given in bits per second while file sizes are stored in bytes. So the number shown by your connection will appear to be about eight times larger than the actual download rate. To convert from bits per second to bytes per second, divide by 8.

Calculating time for downloads and uploads

Time is the result of file size divided by bandwidth, assuming both are using the same base unit. The file will be converted to bits, speed is given in bits per second and then division takes place.

For example, downloading a 500 MB file with a 5 Mbps connection. The size of the file is 4000 Megabits, which is equal to 500 times 8. If you divide 4000 by 5, it becomes 800 seconds or 13 minutes and 20 seconds. As these are all related to each other in size, speed and time, if any two of them are known then the third can be calculated. When you enter file size and time into the tool, it will show the speed.

Data unit conversion

The conversion tool will simultaneously show the same value in all common units from bits to terabytes. It uses decimal units following the convention used in networking and storage where each increase is by a factor of 1000. 1 kilobyte is 1000 bytes, 1 megabyte is 1000 kilobytes, and so on.

On Windows some sizes are reported in binary form, so what is referred to as "megabytes" there actually equals 1048576 bytes (more precisely a mebibyte). The number of bits is the same, only the unit is different. So sometimes the displayed file size may be slightly smaller than the decimal value given here.

Estimating your website's bandwidth requirements

The data volume required by a website is the product of page views and average page size, with a redundancy factor to account for overhead. The average page size includes all content that is loaded on access, including HTML, images, scripts, and stylesheets.

Don't forget the bots. The traffic from search engine crawlers and scraping tools can exceed that of human visitors, so a redundancy factor is used to create an estimated buffer for bots, retries, and traffic spikes. A factor of 2 is a good starting point.

Conversion of monthly limit to speed

Hosting packages often list monthly data allowance while network devices are listed in bits per second. To compare the two values, the monthly data allowance must be evenly distributed over the entire month and then converted to a speed.

If you calculate using 30-day months, a sustained data rate of 1000 GB equates to about 3.09 Mbps. This is an average and not peak performance. As actual data transfer will occur during busy times, the connection must be able to handle much higher peaks.

Typical connection speeds

Concrete examples help to better understand abstract numbers. These are nominal values and the actual transmission rate is usually lower.

Relevant bandwidth tools

The importance of bandwidth varies by application area. Video surveillance planners estimate storage and network requirements based on the resolution and frame rate of cameras, while streaming tools estimate required upload bandwidth for streaming. Display engineers calculate uncompressed signal bandwidths based on display resolution, refresh rate, and color depth. These are specialized calculations, whereas this tool focuses on general networks, downloads, and hosting.