Calculate propeller thrust from diameter and RPM using a typical thrust coefficient, or from disk area and air velocities, in newtons, grams or pounds.

Uses a typical thrust coefficient of 0.10 and sea-level air; change them under assumptions.

Propeller and air assumptions
Typical static Ct for small fixed-pitch props is about 0.08–0.15 (UIUC propeller data). 0.10 is a mid value.

Default 1.225 kg/m³ is standard sea-level air at 15 °C.

Propeller Thrust Formula

The following formula is used to calculate a propeller thrust.

F = .5 × p × A × (Ve2 – Vo2)
  • Where F is the propeller thrust/force (N)
  • p is the density of the air (kg/m3)
  • A is the cross-sectional area of the propeller (m2)
  • Ve is the exit velocity of the air (m/s)
  • Vo is the velocity of the aircraft (m/s)

To calculate the propeller thrust, multiply the density by the cross-sectional area, then multiply by the difference of the squares of the exit velocity and aircraft velocity, then divide by 2.

What is propeller thrust?

Definition:

A propeller thrust is the total amount of force generated by a rotating propeller on an aircraft that causes forward motion.

How to calculate propeller thrust?

Example Problem:

The following example problem outlines the steps and information needed to calculate a propeller thrust.

First, determine the cross-sectional area of the propeller. This is the cross-sectional area from tip to tip of the propeller. For this example, the cross-sectional area is measured to be 3 m2.

Next, determine the density of the fluid. In this case, we will assume air at standard temperature and pressure. This has a density of 1.225 kg/m3.

Next, determine the exit velocity of the air moving out of the propeller enclosure. In this example, the exit velocity is 75 m/s.

Next, determine the speed of the aircraft. This aircraft is moving at a speed of 50 m/s.

Finally, calculate the propeller thrust using the formula above:

F = .5 * p * A * (Ve2 – Vo2)

F = .5 * 1.225 *3 * (752 – 502)

F = 5742.1875 N