Below are some formulas to help you range a target with a scope and reticle.
Further, we atached photos of ranging cheat sheets with common object sizes to help you range quickly and accurately. On the left size is the size of the target in your scope. Top is the objects known size, and in the middle is the distance the target is at from you.
You must know your reticle dimensions and how to mil a target for this to be any use. YouTube is your friend.
Enjoy

0.1 mil = 0.34 moa
1 moa = 0.29 mil

Meter = 1.09 yd
Yard = 0.91 m
Centimeter = 0.39 in
Inch = 2.54 cm

•Range in meters
[Known size (cm) x 10]/mils

•Range in yards with mils
[Size (inches) x 27.78] / mils

•Range in yards with moa
[Size of target in inches x100]/moa