Bandwidth Calculator: Download Time, Speed Needed and Data Transferred
Work out how long a file takes to download or upload at a given speed, the speed you need to move data in a set time, or how much data a connection carries over a time you set in seconds, minutes, hours or days.
Transfer time is data size divided by speed, once both are in the same unit. A byte is 8 bits, so 1 GB is 8,000 megabits, and at 100 Mbps it takes 80 seconds, or 1 min 20 s. To find the speed you need, divide the size by the time; to find the data moved, multiply the speed by the time.
This calculator does not test or measure your connection; it only does the arithmetic on the speed you enter. Real transfers vary with network congestion, Wi-Fi signal, server limits and protocol overhead, so treat the time as a best case at that speed, or lower the efficiency to allow for a slower link.
Transfer time
1 min 20 s
80 seconds in all
1 byte = 8 bits. kB, MB, GB are powers of 1,000; KiB, MiB, GiB are powers of 1,024 (NIST).
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About the Bandwidth Calculator
Bandwidth sums go wrong at the units, so this calculator converts everything to bits first. Two things trip people up. The first is bits against bytes: one byte is 8 bits, so a speed in megabits per second (Mbps) moves an eighth as many megabytes (MB) each second. The second is decimal against binary prefixes. In the SI system kilo, mega and giga mean powers of 1,000, so 1 GB is 1,000,000,000 bytes. In December 1998 the IEC approved separate binary prefixes, kibi, mebi and gibi, for powers of 1,024, so 1 GiB is 1,073,741,824 bytes, as NIST's page on binary prefixes sets out. A file reported as 1 GiB is about 7.4% bigger than 1 GB, and at 100 Mbps it takes 85.9 seconds instead of 80. Choose what to solve for: the transfer time from a size and a speed, the speed needed to move a size in a time, or the data moved at a speed over a time. At 100 Mbps for one hour that is 45 GB. The efficiency box lets you allow for protocol overhead or a connection that runs below its rated speed: at 80%, the 80-second transfer takes 100 seconds.
Frequently asked questions
What is the difference between Mbps and MB/s?+
Mbps is megabits per second and MB/s is megabytes per second. A byte is 8 bits, so divide Mbps by 8 to get MB/s: 100 Mbps is 12.5 MB/s. That is why a 100 Mbps connection moves a 1 GB file in 80 seconds rather than 10.
Why does my computer show a file as smaller than the size I expected?+
Some software counts in binary units (powers of 1,024) but labels them GB. A drive or file of 1,000,000,000 bytes is 1 GB in SI units but only about 0.93 GiB in binary units. The calculator offers both, so pick the unit that matches the number you are reading: GB and MB for powers of 1,000, GiB and MiB for powers of 1,024.
What speed do I need to move 4 GB in 10 minutes?+
Choose speed needed, enter 4 GB and 10 minutes. 4 GB is 32,000 megabits, and 600 seconds gives about 53.3 Mbps, or 6.67 MB/s. Set efficiency below 100% if the link will not run at its full rated speed.
How much data does a connection use in a month?+
Choose data moved, enter the speed and the time. A link running flat out at 10 Mbps for 30 days moves 3.24 TB. Real use depends on how long the link is busy, so if you know the average speed, enter that instead.
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