Airfoil Thickness Calculator

Airfoil thickness shapes almost every wing decision. Whether you're sketching a supersonic fighter or sizing the wing of a Cessna, the thickness-to-chord ratio sets how much room you have inside the wing for structure, how much drag the wing makes, and how it behaves as it nears a stall. Enter the maximum thickness and chord length of any airfoil to get its thickness ratio, or enter the ratio with one length to find the other.

It's the same ratio you reach for when reading a NACA airfoil designation or comparing one wing design against another.

What is airfoil thickness?

An airfoil is the cross-sectional shape of a wing, blade, or fin. The chord length is the straight-line distance from the leading edge (nose) to the trailing edge (tail). The maximum thickness is the greatest distance between the upper and lower surfaces, measured perpendicular to the chord line.

The thickness ratio (often written as $t/c$) expresses the maximum thickness as a percentage of the chord length. A wing with a chord of 5 meters and a maximum thickness of 0.6 meters has a thickness ratio of 12%. That single number captures how thick the airfoil is relative to its length, and a lot of the design follows from it.

Thicker airfoils ($t/c > 12\%$) provide more internal volume for fuel tanks, landing gear bays, and structural spars. They also tend to generate more lift at low speeds and stall more gently. Thinner airfoils ($t/c < 8\%$) reduce wave drag at transonic and supersonic speeds, which is why fighter jets use razor-thin wings compared to cargo planes.

How to use this calculator

Enter any two of the three values and read the third. Each length field has its own unit dropdown (meters, centimeters, millimeters, feet, or inches), and the thickness ratio always comes back as a percentage.

Say your wing chord is 3 meters and you're targeting a 12% thickness ratio. Leave the maximum thickness field empty and you get 0.36 meters. Going the other way, measure the chord and maximum thickness off an existing wing and you read the t/c percentage straight off. The line chart underneath plots how the thickness ratio changes across chord lengths for the maximum thickness you entered.

Understanding the formula

It comes down to one division:

Where $t$ is the maximum thickness and $c$ is the chord length, both measured in the same units. The result is a dimensionless percentage.

Rearrange it to solve for either length:

Take the Boeing 737. Its wing root has a chord of roughly 5 meters, and with a supercritical airfoil around 12% thickness ratio, the maximum thickness works out to:

That's 60 centimeters of internal space, enough for fuel tanks and the main landing gear.

Compare that to an F-16 Fighting Falcon: a wing chord near 2 meters with a thickness ratio around 4%.

Only 8 centimeters thick. The wing is essentially a blade, optimized purely for low drag at supersonic speeds. The trade-off: less internal room for fuel means the F-16 relies on external fuel tanks mounted on pylons.

Applications in aircraft design

In preliminary wing design, picking the t/c ratio early locks in constraints on fuel volume, structural weight, and aerodynamics all at once. A thicker wing can use lighter spar material without getting heavy; a thinner one needs stronger material to carry the same bending loads in less depth.

It also decodes NACA airfoils. The last two digits of a NACA 4-digit designation are the thickness ratio: NACA 2412 sits at 12%, and the symmetric NACA 0006 is 6%. Once you know that, you can read any 4-digit profile at a glance.

Wind turbine blades show the whole range in a single part. Root sections run thick (up to 40% t/c) for strength and taper to around 15% at the tip for efficiency, and the same calculation covers both ends.

Aircraft and marine propellers follow the same pattern, thick at the root and thinner toward the tip.

Practical tips

If you're doing the math by hand, keep both lengths in the same unit system. The ratio is dimensionless, so mixing meters and feet quietly gives you the wrong answer. This tool converts units for you, so entering thickness in centimeters and chord in feet is fine.

For NACA 4-digit airfoils, you don't need to calculate anything: the last two digits are the thickness ratio. NACA 0015 means 15%.

Real wings taper along the span, so the t/c ratio changes from root to tip. When you report a thickness ratio, say which spanwise station it's measured at.

Frequently asked questions

What is a typical thickness ratio for commercial aircraft?

Most commercial airliners use supercritical airfoils with t/c ratios between 10% and 14%. The wing root is usually thicker than the tip to make room for landing gear and fuel.

Can the thickness ratio exceed 100%?

Not on anything that flies. That would mean the airfoil is thicker than it is long. Real values run from about 3% on supersonic fighters to 40% at the root of a wind turbine blade.

Does a higher thickness ratio always mean more drag?

Not necessarily. At low speeds, a moderately thick airfoil can produce less total drag than a very thin one because it generates lift more efficiently. The drag penalty for thickness only turns severe at transonic and supersonic speeds, where shockwaves dominate.

How does thickness ratio affect stall behavior?

Thicker airfoils tend to stall more gradually, giving pilots warning through buffeting before the full stall. Very thin airfoils can stall abruptly with little warning, so they need more careful handling at high angles of attack.