Ground Speed Calculator

Determine true ground speed based on airspeed and wind conditions.

Enter the aircraft's true airspeed, the prevailing wind speed, and the angle of the wind relative to your course to calculate the resulting ground speed.

Practical Examples

Explore these common scenarios to see how wind affects ground speed.

Cessna 172 with Headwind

General Aviation

A typical scenario for a small aircraft flying against the wind.

TAS: 120 knots, Wind: 15 knots @ 30°

Airliner with Tailwind

Commercial Flight

Illustrates how a tailwind can significantly increase an airliner's ground speed.

TAS: 480 knots, Wind: 50 knots @ 160°

DJI Drone with Crosswind

Drone Operation

Calculating the effect of a direct crosswind on a drone's flight.

TAS: 35 mph, Wind: 10 mph @ 90°

Complex Wind Scenario

Flight Training

A complex case with a strong wind from an oblique angle, converted to km/h.

TAS: 250 kmh, Wind: 40 kmh @ 135°

Other Titles
Understanding Ground Speed: A Comprehensive Guide
An in-depth look at the principles of ground speed, its calculation, and its importance in aviation and navigation.

What is Ground Speed?

  • The Basics of Motion
  • Airspeed vs. Ground Speed
  • The Role of Wind
Ground speed is the horizontal speed of an aircraft relative to the Earth's surface. It's a crucial metric for navigation, as it determines how quickly an aircraft will reach its destination. Unlike airspeed, which is the speed relative to the surrounding air mass, ground speed accounts for the effect of wind.
The Critical Difference: Airspeed vs. Ground Speed
An aircraft's engine and aerodynamic design determine its true airspeed (TAS). However, if the air mass itself is moving (i.e., there is wind), the aircraft's speed over the ground will be different. A tailwind (wind blowing in the same direction as the aircraft) increases ground speed, while a headwind (wind blowing against the aircraft) decreases it. A crosswind will push the aircraft sideways and also affect its ground speed.

Simple Scenarios

  • No Wind: If there is no wind, Ground Speed = True Airspeed.
  • Direct Tailwind: With a 150-knot airspeed and a 20-knot tailwind, Ground Speed = 170 knots.
  • Direct Headwind: With a 150-knot airspeed and a 20-knot headwind, Ground Speed = 130 knots.

Step-by-Step Guide to Using the Ground Speed Calculator

  • Inputting Your Data
  • Interpreting the Results
  • Unit Conversion
Our calculator simplifies a complex vector problem into a few easy steps. Here's how to use it effectively:
1. Enter True Airspeed (TAS)
This is the speed of your aircraft without any wind effect. You can typically find this in the aircraft's pilot operating handbook (POH).
2. Enter Wind Speed and Angle
Input the speed of the wind and its angle relative to your flight path. An angle of 0° represents a direct headwind, while 180° is a direct tailwind.
3. Select Units
Choose your preferred unit of speed (Knots, mph, or km/h). The calculator will apply this unit to all inputs and outputs for consistency.
4. Analyze the Output
The calculator provides three key pieces of information: the final Ground Speed, the Headwind/Tailwind component (positive for headwind, negative for tailwind), and the Crosswind component.

The Mathematical Derivation and Formulas

  • Vector Addition
  • The Law of Cosines
  • Component Breakdown
Ground speed is the magnitude of the vector sum of the aircraft's velocity vector and the wind's velocity vector. The calculation can be performed using the Law of Cosines.
Formula Using Law of Cosines
Given TAS (True Airspeed), WS (Wind Speed), and WA (Wind Angle relative to the course), the ground speed (GS) is calculated as: GS = √[ (TAS)² + (WS)² - 2 TAS WS * cos(WA) ]. Our calculator uses this principle.
Headwind and Crosswind Components
The wind's effect can be broken down into two parts: a component that acts along the aircraft's path and a component that acts perpendicular to it. Headwind = WS cos(WA). Crosswind = WS sin(WA). Note that a negative headwind value indicates a tailwind.

Calculation Example

  • TAS = 200, WS = 30, WA = 60°
  • Headwind = 30 * cos(60°) = 15
  • Crosswind = 30 * sin(60°) ≈ 25.98
  • Ground Speed = √[ (200 - 15)² + (25.98)² ] ≈ √[ 185² + 25.98² ] ≈ 186.8 knots

Real-World Applications of Ground Speed

  • Flight Planning
  • Fuel Calculation
  • Search and Rescue
Understanding ground speed is not just an academic exercise; it has critical real-world implications.
Flight and Fuel Planning
Pilots use ground speed to calculate their estimated time of arrival (ETA) and the amount of fuel required for a trip. A stronger-than-expected headwind can significantly increase fuel consumption and potentially require an unplanned stop.
Navigation and Course Correction
Crosswinds push an aircraft off its intended course. By calculating the crosswind component, pilots can determine the necessary 'crab angle' to adjust their heading and maintain the correct track over the ground.

Common Misconceptions and Key Considerations

  • True vs. Indicated Airspeed
  • Magnetic vs. True North
  • Wind's Effect on Turns
There are several nuances to consider when working with these calculations.
True Airspeed (TAS) vs. Other Airspeeds
Do not confuse True Airspeed (TAS) with Indicated Airspeed (IAS) or Calibrated Airspeed (CAS). TAS is corrected for air density (altitude and temperature) and is the correct value to use for ground speed calculations.
Direction and Headings
For precise flight planning, pilots must account for the difference between magnetic north (what a compass shows) and true north (used on maps), as well as instrument errors. Our calculator simplifies this by using a relative wind angle, but in a real cockpit, these factors are vital.