Aspect Ratio
Ratio of wingspan squared to wing area; higher AR reduces induced drag.
Formula
Variables
Example
b=10 m, S=16 m²: AR = 6.25
How it works
Aspect ratio measures how long and slender a wing is by comparing span to area. Because induced drag is tied to the strength of wingtip vortices, a wing with more span for the same area spreads lift over a larger distance and usually produces weaker vortex-induced downwash, which is why higher aspect ratio wings are generally more aerodynamically efficient at low speeds. In practice, the formula turns a wing’s geometry into a single number that helps compare designs with very different shapes.
When to use it
Use this when comparing wing designs, estimating aerodynamic efficiency, or analyzing how wing geometry affects induced drag in aircraft, gliders, and UAVs. It is especially useful in preliminary design, performance studies, and when checking whether a wing is relatively stubby or slender.
Worked example, step by step
Given: wingspan b = 18 m and wing area S = 27 m² Step 1: Square the wingspan: b² = 18² = 324 m² Step 2: Divide by wing area: AR = b² / S = 324 / 27 Step 3: Compute the result: AR = 12 Final answer: The wing aspect ratio is 12
Common mistakes to avoid
- Using the total aircraft length instead of wingspan for b
- Forgetting to square the wingspan before dividing by wing area
- Mixing units for b and S, which makes the result meaningless
Did You Know?
High-aspect-ratio wings, like a glider's or the U-2 spy plane's, minimize drag for maximum range.
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