Mean Aerodynamic Chord (MAC) Calculator

Calculation Results

Taper Ratio (λ): -
MAC Length: -
Distance from Root (Y-MAC): -
MAC LE Longitudinal Offset (X-MAC): -

What is the Mean Aerodynamic Chord (MAC)?

The Mean Aerodynamic Chord (MAC) is a critical concept in aerodynamics and aeronautical engineering. It represents the chord of an imaginary rectangular wing that would have the same aerodynamic characteristics as the actual wing under study. For most aircraft, the wing is not a perfect rectangle; it usually tapers from the root (where it joins the fuselage) to the tip. The MAC provides a single reference length used to define the aerodynamic center and the longitudinal stability of the aircraft.

MAC = Cr * (2/3) * ((1 + λ + λ²) / (1 + λ))

Why is MAC Important for Aircraft Stability?

Understanding the MAC is essential for calculating the Center of Gravity (CG) limits. Most aircraft manuals define the CG range as a percentage of the MAC (e.g., "CG must be between 15% and 25% MAC"). If the CG is too far forward, the aircraft becomes overly stable and difficult to rotate; if it is too far aft, the aircraft may become unstable and impossible to recover from a stall. By knowing the exact length and position of the MAC, engineers can ensure the aircraft operates within safe limits.

How to Use the MAC Calculator

To use this tool, you will need the primary dimensions of your wing planform:

  • Root Chord (Cr): The distance from the leading edge to the trailing edge at the wing's center.
  • Tip Chord (Ct): The chord length at the very end of the wing tip.
  • Wing Span (b): The total distance from tip to tip.
  • Sweep Offset: The longitudinal distance the tip leading edge is set back from the root leading edge (useful for swept wings).

Frequently Asked Questions

What is the Taper Ratio?

The taper ratio (λ) is the ratio of the tip chord to the root chord (Ct / Cr). A taper ratio of 1.0 means the wing is a perfect rectangle. Smaller values indicate a more aggressive taper toward the tip.

Where is the MAC located?

The MAC is located at a specific spanwise distance from the root, often called Y-MAC. For a trapezoidal wing, this is usually about 40-45% of the semi-span from the root, depending on the taper ratio. Our calculator provides both the length of the MAC and its physical location relative to the root chord.