I see. That’s the same as converting “Beats Per Minute” (BPM) to “Beat Length”.
"Beat Length (seconds) = 60 / “BPM”
“BPM” = 60 / “Beat Length (seconds)”
Example:
If Beat length = 0.5 seconds
then BPM = 60 / 0.5 = 120
If BPM = 120
then Beat Length = 60 / 120 = 0.5
If you need to do a lot of these calculations, there’s a “Quick Calculator” plug-in that includes BPM to Beat Length conversion: https://forum.audacityteam.org/t/quick-conversion-calculator/15589/1 (If you want to try it, be sure to download the “Current version” rather than the Obsolete version)