About this tool
Internet connections are sold in megabits per second (Mbit/s), but file sizes are given in megabytes or gigabytes. Because a byte has eight bits, downloading 1 GB over a 100 Mbit line takes not 10 but at least 80 seconds. The bandwidth calculator does this conversion for you.
It calculates how long a transfer takes, which bandwidth you need for an amount of data in a given time – e.g. for a nightly backup – and converts data rates between bit/s and byte/s. An adjustable overhead accounts for the share of the rate used by protocols and Wi-Fi. Convert storage sizes in other units with the Unit Converter.
How it works
- Choose whether you need the download time, the required bandwidth or a conversion.
- Enter the data size and speed or the available time with matching units.
- For the download time, set the expected overhead, e.g. 10 % for Wi-Fi.
- Read the result and copy it if needed.
Frequently asked questions
What is the difference between Mbit/s and MB/s?
Mbit/s means megabits, MB/s megabytes per second. A byte has 8 bits, so 100 Mbit/s equals 12.5 MB/s. Download programs usually show MB/s, providers advertise Mbit/s.
Why does my download take longer than calculated?
The advertised speed is a maximum. Protocol overhead (TCP/IP, encryption), Wi-Fi interference, other devices on the network and the speed of the server reduce the actual rate. An overhead of 10–20 % is normal.
What do KiB, MiB and GiB mean?
These are binary prefixes: 1 KiB = 1024 bytes, 1 MiB = 1024 KiB. Disk vendors, by contrast, count in steps of 1000. That is why Windows shows a 1 TB disk as about 931 “GB” – meaning GiB.
How much bandwidth do I need for video streaming?
As a rule of thumb: about 5 Mbit/s for HD, 15–25 Mbit/s for 4K per stream. With the “Required bandwidth” mode you can also work out which connection you need for a backup or a large upload in a given time.