Calculating Rate of Descent on Final

This is from the thread you posted 2 years ago

➡ Rule of thumb for the descent is:

If you are flying at 18000ft at a ground speed of 200kts and you need to descend to 3000ft, the difference is 15000ft. Multiply 15 x 3 = 45 miles out you must begin your descent. Half your ground speed is 100, add a zero, and 1000 ft per minute is your rate
of descent.

😉

okay, how would you calculate if you were 15 miles from touchdown and you are going 200kts at 9000 feet.?

At what altitude is your runway? Another thing is that your speed will decrease while descending.

lets says runway is at sea level and lets say i will be descending at 200kts to make numbers easy..

Descent rate would be 1000ft/min and you would start 27 miles out.