Solve propeller blade angle, pitch, or diameter with mixed metric and imperial units, station-specific helix geometry, pitch-to-diameter ratio, and blade-angle table.

Ideal constant-pitch helix geometry. Blade angle is measured from the plane of rotation, not the angle of attack. Use manufacturer data for real propeller setup.

100% uses the blade tip; 75% uses three quarters of the tip radius.

Related Calculators

Propeller Angle Formula

At the selected blade station, geometric pitch relates blade angle to the local circumference. Select the value to solve, enter the two known quantities, and choose the blade station. The examples below use the default 100% station.

theta = arctan(P / (pi × D × s))
P = tan(theta) × pi × D × s
D = P / (pi × s × tan(theta))
  • theta = propeller angle, in radians inside the trigonometric functions
  • P = propeller pitch
  • D = propeller diameter
  • pi = approximately 3.14159; s = blade station as a fraction of tip radius (100% = 1)

If you enter pitch and diameter, the calculator solves for propeller angle using the arctangent formula. If you enter angle and diameter, it solves for pitch. If you enter angle and pitch, it solves for diameter. Pitch and diameter must use the same length basis in the formula, so the calculator converts inches and millimeters as needed.

Common Unit Conversions for Propeller Angle Calculations

Conversion Multiplier Use
Millimeters to inches mm × 0.0393701 Convert pitch or diameter to inches
Inches to millimeters in × 25.4 Convert a calculated length back to mm
Degrees to radians degrees × pi / 180 Use angle in tangent formulas
Radians to degrees radians × 180 / pi Display angle in degrees

Typical Propeller Angle Ranges

Angle General meaning
Low angle Lower pitch relative to diameter
Medium angle Balanced pitch-to-diameter relationship
High angle Higher pitch relative to diameter

Example Propeller Angle Calculations

Example 1: Calculate propeller angle

Suppose the propeller pitch is 10 inches and the propeller diameter is 12 inches.

theta = arctan(10 / (pi × 12))
theta ≈ 0.2593 radians ≈ 14.856 degrees

The propeller angle is about 14.86 degrees.

Example 2: Calculate propeller pitch

Suppose the propeller angle is 15 degrees and the propeller diameter is 12 inches.

15 degrees = 0.2618 radians
P = tan(0.2618) × pi × 12
P = 10.101 inches

The propeller pitch is about 10.10 inches.

Propeller Angle Calculator FAQ

What is propeller angle?

Blade angle is measured between the blade section and the plane of rotation. The local circumference is pi × diameter × s, where s is the selected station fraction of tip radius. The default 100% station uses s = 1.

Does pitch need to be in the same unit as diameter?

Yes. Pitch and diameter must be in the same length unit before applying the formula. If pitch is in inches and diameter is in millimeters, one value has to be converted first. The calculator handles inch and millimeter conversions for you.

Why are radians used in the formula?

Trigonometric formulas such as tangent and arctangent use radians as the standard angle measure. You can still enter or read the angle in degrees, but the angle is converted to radians when used inside the formula.