Ground Speed
Calculate an aircraft's ground speed from true airspeed, wind speed, course, and wind direction. Free online aviation calculator with wind correction angle, heading, and interactive charts.
Direction the wind is blowing toward (not from). 0° = North, 90° = East, 180° = South, 270° = West.
About This Calculator
The Ground Speed Calculator helps pilots, student aviators, and aviation enthusiasts compute an aircraft's speed over the ground based on true airspeed and wind conditions. Understanding ground speed is essential for flight planning, fuel calculations, and estimating time en route.
This calculator uses standard vector addition formulas from aviation navigation. The ground speed is computed as the vector sum of true airspeed and wind speed. The wind correction angle (WCA) is the angular adjustment needed to counteract crosswind drift, calculated using arcsin(crosswind component / true airspeed). The heading is the sum of course and WCA, giving the direction the aircraft must point to maintain the desired ground track.
Key Formulas
Wind Correction Angle: α = arcsin(Wcross / TAS) where Wcross = WS × sin(WindDir − Course)
Ground Speed: GS = TAS × cos(α) + WS × cos(WindDir − Course)
Heading: ψ = Course + α
How to Use
Enter your aircraft's true airspeed in knots, the wind speed and direction (direction the wind is blowing toward, not from), and your desired course. The calculator will display the ground speed, wind correction angle, heading, and the headwind/crosswind components. Use the chart tabs to visualize the speed components or see how ground speed varies with changing wind direction.
Aviation Context
In aviation, true airspeed (TAS) increases with altitude due to reduced air density. Ground speed determines actual travel time over the ground and is used for fuel planning and estimated time of arrival. A headwind reduces ground speed, increasing flight time, while a tailwind has the opposite effect. Crosswinds require a wind correction angle that also slightly reduces ground speed.
Frequently Asked Questions
What is ground speed in aviation?
Ground speed is the horizontal speed of an aircraft relative to the Earth's surface. It is the vector sum of true airspeed and wind speed, and is used to calculate flight duration and fuel consumption.
How is ground speed different from true airspeed?
True airspeed (TAS) is the speed of the aircraft relative to the surrounding air mass. Ground speed is TAS adjusted for wind effects. In still air they are equal, but with a headwind ground speed is lower than TAS, and with a tailwind ground speed is higher.
What is wind correction angle?
Wind correction angle (WCA) is the angle the pilot must point the aircraft into the wind to maintain the desired course over the ground. It is calculated as arcsin(crosswind component / true airspeed).
How does wind direction affect ground speed?
Wind blowing directly from behind (tailwind) increases ground speed, wind from ahead (headwind) decreases it, and crosswind reduces ground speed slightly due to the angle correction needed to maintain course.
What is the difference between course and heading?
Course is the intended path of the aircraft over the ground measured clockwise from North. Heading is the direction the aircraft's nose points, which differs from course by the wind correction angle to compensate for wind drift.
What units does this calculator use?
This calculator uses knots for airspeed and wind speed, and degrees for course and wind direction. Angles are measured clockwise from true North (0° to 360°). Wind direction is the direction the wind is blowing toward, not from.
Can this calculator be used for flight planning?
Yes, this calculator is useful for basic flight planning. Enter your planned true airspeed, forecast wind conditions, and desired course to compute ground speed, wind correction angle, and heading for navigation.
How accurate is the ground speed calculation?
The calculation uses standard vector addition formulas from aviation navigation. Results are rounded to 2 decimal places. Actual in-flight ground speed may vary due to wind gusts, altitude changes, and true airspeed variations.