LoRa calculator - Online and standalone

Semtech provides a “LoRa Calculator” to get different useful values such the Time on Air or power consumption. This software used to be standalone (.exe) and there is now a on-line version here : . For educational purposes, I’m only interested in the Time on Air.

When using the SX1261 transceiver, the “LoRa calculator” got this answer for this specific configuration:

The Time on Air and the symbol time are correct, however the total length is incorrect as 37,25 x1,024 doesn’t match with 46,33 ms. Whatever the parameters, the “total length” value is always 8 less than it should be. So first question: why?

Now, I want to try the online version, of course with the same parameters:

And the results are as followed.

Now only the symbol time is correct. The Time on Air and number of symbols are incorrect.

There are too many errors for just being mistakes. So I’m wondering what I’ve missed.

Thanks for your help.


Thanks for the feedback Sylvain…we’re working to address the issues and will hopefully have a newer build of the Calculator out this week.