EYEPIECE  FIELD  OF  VIEW 
Actual Field of View = Eyepiece Apparent Field of View Divided by
[Magnification] Telescope Focal Length Divided by Eyepiece Focal Length

  BINOCULAR  FIELD  OF  VIEW 
X ft / 1,000 yds     [Feet at 1,000 Yards]
Divide X by 52.4

Metric
X Meters at 1,000 Meters
Divide X by 16