✈️ Ground Speed Calculator
Calculate ground speed
How to Use This Calculator
Enter True Airspeed
Input the aircraft's true airspeed (TAS) in m/s. This is the speed relative to the air mass. Convert from knots by multiplying by 0.514 (e.g., 100 knots = 51.4 m/s).
Enter Wind Speed
Enter the wind speed in m/s. This is how fast the air mass is moving relative to the ground. Convert from km/h by dividing by 3.6.
Enter Wind Angle
Input the wind angle in degrees. 0° = headwind (wind from front), 90° = crosswind (wind from right), 180° = tailwind (wind from behind), 270° = crosswind (wind from left).
Click Calculate
Press "Calculate" to find the ground speed - the actual speed over the ground, accounting for wind effects.
Formula
v_wx = v_w × cos(θ)
v_wy = v_w × sin(θ)
GS = √((TAS + v_wx)² + v_wy²)
Where:
- TAS = True Airspeed (m/s) - speed relative to air
- v_w = Wind speed (m/s)
- θ = Wind angle (degrees from head-on)
- v_wx = Wind component along flight path (m/s)
- v_wy = Wind component perpendicular to flight path (m/s)
- GS = Ground speed (m/s) - speed relative to ground
Example Calculation:
Aircraft at 50 m/s TAS with 10 m/s wind at 45° (crosswind from right):
1. Wind components: v_wx = 10 × cos(45°) = 7.07 m/s, v_wy = 10 × sin(45°) = 7.07 m/s
2. Ground speed: GS = √((50 + 7.07)² + 7.07²) = √(3259 + 50) = 57.6 m/s
Headwind reduces ground speed, tailwind increases it. Crosswinds cause drift but have less effect on ground speed.
About Ground Speed Calculator
The Ground Speed Calculator determines an aircraft's speed over the ground by combining true airspeed (speed through air) with wind velocity. Ground speed differs from airspeed because the air itself is moving relative to the ground, and this affects travel time and fuel consumption.
Airspeed vs. Ground Speed
- True Airspeed (TAS): Speed of the aircraft relative to the air mass. This is what the aircraft's engine and aerodynamics determine.
- Ground Speed (GS): Speed relative to the ground. This determines actual travel time and is what GPS measures. GS = TAS + wind effect.
- Key Difference: With a tailwind, ground speed exceeds airspeed. With a headwind, ground speed is less than airspeed. Crosswinds cause drift but have minimal effect on ground speed.
Wind Effects
Headwind (0°): Wind from ahead reduces ground speed. A 50 m/s aircraft with 10 m/s headwind has 40 m/s ground speed - takes longer to reach destination.
Tailwind (180°): Wind from behind increases ground speed. A 50 m/s aircraft with 10 m/s tailwind has 60 m/s ground speed - arrives faster.
Crosswind (90° or 270°): Wind from the side causes drift but minimal ground speed change. Pilots must adjust heading to compensate for drift.
Practical Applications
- Flight Planning: Calculate flight times and fuel requirements based on ground speed, which determines how long the trip actually takes.
- Navigation: Determine course corrections needed to compensate for wind drift and maintain desired track.
- Fuel Management: Ground speed affects flight duration - crucial for calculating fuel consumption and range.
- ATC Operations: Air traffic controllers use ground speed for spacing aircraft and planning approaches.
- Weather Analysis: Understand how wind patterns affect aircraft performance and flight efficiency.
Understanding the Results
Ground speed is calculated using vector addition: the aircraft's velocity through the air plus the wind velocity. The calculator resolves wind into components parallel and perpendicular to the flight path, then combines them vectorially with true airspeed.
Frequently Asked Questions
What's the difference between airspeed and ground speed?
Airspeed is speed relative to the air (what the aircraft "feels"). Ground speed is speed relative to the ground (what determines travel time). With a tailwind, ground speed > airspeed. With a headwind, ground speed < airspeed. They're equal in still air.
How does wind angle affect ground speed?
Headwinds (0°) reduce ground speed the most. Tailwinds (180°) increase it the most. Crosswinds (90°, 270°) cause drift but have minimal effect on ground speed - only the component parallel to the flight path matters for speed.
Why is ground speed important?
Ground speed determines actual travel time and fuel consumption. A flight that takes 2 hours with no wind might take 2.5 hours with a headwind or 1.5 hours with a tailwind. This directly affects flight planning and fuel requirements.
How do I convert between knots and m/s?
1 knot = 0.514 m/s (approximately). So multiply knots by 0.514 to get m/s, or divide m/s by 0.514 to get knots. For example, 100 knots = 51.4 m/s, and 50 m/s = 97.3 knots.
Can ground speed ever be negative?
Ground speed is always positive (magnitude of velocity). However, if a very strong headwind exceeds airspeed, the aircraft would move backward relative to the ground - but the calculator shows the magnitude of the resulting velocity vector.
What about drift angle?
This calculator shows ground speed but not drift angle. Drift is caused by crosswind components and requires additional calculation to determine the heading correction needed to maintain the desired track over ground.