What Are Airfoil Coordinates and How Do You Find and Use Them?

Airfoil coordinates are the ordered x/y point pairs that define an airfoil section's outline: x runs along the chord and y gives the surface offset, so the same list of points describes both the upper and lower surface of the shape. On Airfoil Tools you can find coordinates by searching a database of 1,638 airfoils, download them as a dat file, or paste your own points into the tools to plot, compare, or generate sections. The main practical limit is that airfoils you add yourself are stored only in your browser session, so they must be re-added after the browser is reopened.

What the coordinates actually describe

A dat file is a plain list of points, normally ordered from the trailing edge along one surface to the leading edge and back along the other. Each line is an x value and a y value. Because the points trace the section outline, they carry the two properties most searches filter on:

• Thickness — the maximum distance between the upper and lower surface, usually expressed as a percentage of chord.
• Camber — the curvature of the mean line between the surfaces, also as a percentage of chord.

A symmetrical section has zero camber, so its upper and lower coordinates mirror each other. Changing chord length scales the coordinates; it does not change the shape.

Finding coordinates in the database

The Airfoil search lets you filter by thickness and camber and shows preview images of the sections, so you can narrow the list before downloading anything. You can also browse by name through the A-to-Z index, which is grouped by first letter (for example, the N entries run from n0009sm to nplx, and the S entries from s1010 to supermarine371ii).

A workable sequence:

1. Set a thickness and camber range that matches your requirement, or search by airfoil name if you already know it.
2. Check the preview image to confirm the shape looks like what you expect.
3. Open the airfoil details page to see polar diagrams across a range of Reynolds numbers.
4. Download the dat file data in the format you need, or use it directly in the tools.
5. Follow the link to the original data source if you need more information about where the section came from.

The site notes a Reynolds number range of 50,000 to 1,000,000, which you can set; that range is the context for the polar data shown on the details pages.

Using coordinates in the tools

Once you have coordinate data, three tools consume it directly:

The plotter output is an SVG plan, which can be printed full size or across multiple pages for large sections. The comparison plan can also be downloaded or printed full size for better resolution.

Adding your own coordinates

If your section is not in the database, use My airfoils: paste the dat file data into the form and the airfoil becomes available in the drop-down menus used by the other tools. This is the route for data from other sources or for sections you generated yourself.

The constraint to plan around: custom airfoils are stored only in your browser session. Close the browser and they are gone, so you need to paste the data again next time. Keep the original dat file somewhere outside the browser so re-adding is a copy-and-paste rather than a re-download.

Choosing between the routes

• Known, standard section — search the database by name, check the preview, download the dat file.
• Section defined by thickness and camber targets — filter the search by those two values, then compare candidates with the comparison tool before committing.
• Section you already have data for — paste it into My airfoils and use it in the plotter or comparison tool.
• Section you want to create from a formula — use the NACA 4 digit or 5 digit generator instead of searching.