How to use this on a job
A 100 MB log and a 100 Mb/s link do not imply a one-second download. File sizes usually count bytes; link speeds count bits. Sort out that factor of eight before blaming the network.
- 01
Select the source unit exactly as written on the file or specification. A capital B means byte. The letter i in MiB means a power-of-two prefix.
- 02
Choose the result unit. The calculation first converts the source to bits, so there is only one conversion path between storage and transmission units.
- 03
Enter the link rate in decimal Mb/s. The displayed duration is a lower bound at that constant payload rate. Real transfers also include headers, acknowledgements, other traffic and device processing.
Work through one example
time [s] = size [bits] ÷ rate [bits/s]
One MiB contains 8,388,608 bits. At a sustained payload rate of 8 Mb/s, it takes 1.048576 seconds. One decimal MB at that same rate takes exactly one second. The difference comes from the prefix, not from a rounding error.
Before you trust the answer
A bus running at its nameplate speed does not deliver that entire rate as useful application data. Do not use the ideal time as a PLC communication watchdog setting. Measure the real transaction cycle and allow for contention and retries.