Departure Angle Calculator - Calculator Academy

Enter the rear ground clearance and rear overhang into the calculator to determine the departure angle.

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Departure Angle Formula

The following formula is used to calculate the departure angle for a given rear ground clearance and rear overhang.

\theta = \arctan\left(\frac{GC}{RO}\right) \times \frac{180}{\pi}

Variables:

θ is the departure angle in degrees
GC is the rear ground clearance (height) in centimeters
RO is the rear overhang (distance from the rear axle to the rearmost point) in centimeters

To calculate the departure angle, divide the rear ground clearance by the rear overhang, then take the arctangent of the result and convert it from radians to degrees.

What is a Departure Angle?

The departure angle is the maximum angle of descent (or ramp angle) a vehicle can negotiate without the rear overhang contacting the ground. It is an important specification for off-road vehicles, as it indicates the vehicle’s ability to descend steep declines and clear obstacles without rear-end damage. The departure angle is influenced primarily by the rear ground clearance and the rear overhang (and rear bumper shape); a higher departure angle generally indicates better off-road capability.

How to Calculate Departure Angle?

The following steps outline how to calculate the Departure Angle.

First, determine the rear ground clearance (GC) of the vehicle in centimeters.
Next, determine the rear overhang (RO) of the vehicle in centimeters (rear axle to rearmost point).
Next, calculate the departure angle using the formula: θ = arctan(GC/RO) × (180/π).
Finally, record the departure angle.
After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem :

Use the following variables as an example problem to test your knowledge.

Ground Clearance (GC) = 30 cm

Rear Overhang (RO) = 100 cm

Follow-Up Calculations

If your truck goes from a 21.8° departure angle to roughly 23.4° after gaining 1 inch of rear ground clearance, that usually comes from fitting a taller wheel-and-tire package. The custom wheel package setup calculator is useful when you want to size a 3-piece setup for more tire diameter without guessing, since even an extra inch of radius can make a noticeable difference at the bumper.

If moving from 33-inch tires to 35-inch tires raises your departure angle by about 1 to 2 degrees, the tradeoff is that the axle now sees about 6% taller gearing, so a 3.73 rear end behaves more like a 3.52. You can recalculate your effective gearing after a tire upgrade to see whether you should regear, because bigger tires can soften acceleration and towing performance.

That same jump from 33-inch to 35-inch tires not only helps clearance under the rear bumper, it also changes wheel speed: at 60 mph, axle RPM drops from about 676 rpm to about 631 rpm on a 3.73 gear set. You can see the RPM change for your setup, which is important for speedometer accuracy and cruise control behavior after a lift or tire swap.