Question makes no sense. A tick is a change in price not a unit of measure. What is the difference "in ticks" between 10 am and 12 pm? Meaningless. Is is 2 hours, 120 minutes, or 7200 seconds, etc.

If you meant "tick size", now you have a unit of measure. (P1-P2)/TS.

Both for crosses of 5 and 3 decimals.

Thank you