API Documentation

Free, public REST API for airfoil data and aerodynamic polars.

Overview

The Foil.tools API provides programmatic access to our database of >1,600 airfoils and their pre-computed aerodynamic polars across a wide range of Reynolds numbers.

Base URL

https://foil.tools/api/v1

Authentication

None required

Rate Limit

60 requests/hour

Rate Limiting

All API responses include rate limit headers to help you track your usage:

X-RateLimit-Limit: 60

X-RateLimit-Remaining: 58

X-RateLimit-Reset: 1710547200 (Unix timestamp)

When the limit is exceeded, the API returns a 429 status with a JSON body containing the reset time.

Endpoints

GET/api/v1

API discovery endpoint. Returns available endpoints, descriptions, and rate limit info.

Example

Request

curl https://foil.tools/api/v1

Response

{
  "version": "1",
  "base_url": "https://foil.tools/api/v1",
  "endpoints": [ ... ],
  "rate_limit": { "requests_per_hour": 60, "auth": "none" }
}

GET/api/v1/airfoils

List airfoils. Without filters returns all 1,600+ profiles. Supports fuzzy name search and geometric filters. Add geometry=1 to include thickness and camber fields.

Parameters

Name	In	Required	Description
q	query	No	Fuzzy name search, e.g. "naca 23" or "eppler".
family	query	No	Filter by series family, e.g. "NACA 4-digit", "Eppler", "Selig".
t_min	query	No	Minimum thickness as a fraction (e.g. 0.10 = 10%).
t_max	query	No	Maximum thickness as a fraction.
camber_min	query	No	Minimum camber as a fraction.
camber_max	query	No	Maximum camber as a fraction.
geometry	query	No	Set to 1 to include thickness and camber values in the response.

Example

Request

curl "https://foil.tools/api/v1/airfoils?family=Eppler&t_min=0.10&t_max=0.14&geometry=1"

Response

{
  "count": 12,
  "airfoils": [
    {
      "name": "Eppler 387",
      "filename": "e387",
      "family": "Eppler",
      "source": "UIUC Database",
      "thickness": 0.0907,
      "camber": 0.0365
    },
    ...
  ]
}

GET/api/v1/airfoils/{name}

Airfoil geometry as Selig-ordered coordinate pairs plus a summary (thickness, camber, TE thickness, LE weight). Add ?format=dat or Accept: text/plain for a raw XFOIL-compatible .dat file.

Parameters

Name	In	Required	Description
name	path	Yes	Airfoil key, e.g. naca2412, e387, s1223. Case-insensitive.
format	query	No	Set to "dat" to return raw Selig .dat text instead of JSON.

Example

Request

curl https://foil.tools/api/v1/airfoils/e387

Response

{
  "name": "e387",
  "display_name": "Eppler 387",
  "family": "Eppler",
  "summary": {
    "max_thickness": 0.0907,
    "max_camber": 0.0365,
    "te_thickness": 0.0,
    "le_weight": 0.172
  },
  "coordinates": [
    { "x": 1.0, "y": 0.00126 },
    { "x": 0.9982, "y": 0.00268 },
    ...
    { "x": 1.0, "y": -0.00126 }
  ]
}

GET/api/v1/polars/{name}

Aerodynamic polar rows (CL, CD, CM vs alpha) for a specific airfoil. Supports range filters on Re, alpha, CL, and CD.

Parameters

Name	In	Required	Description
name	path	Yes	Airfoil key, e.g. naca2412, e387, s1223. Case-insensitive.
re_min	query	No	Minimum Reynolds number (e.g. 200000).
re_max	query	No	Maximum Reynolds number.
alpha_min	query	No	Minimum angle of attack in degrees.
alpha_max	query	No	Maximum angle of attack in degrees.
cl_min	query	No	Minimum lift coefficient.
cl_max	query	No	Maximum lift coefficient.

Example

Request

curl "https://foil.tools/api/v1/polars/naca2412?re_min=500000&re_max=500000&alpha_min=0&alpha_max=8"

Response

{
  "airfoil": "naca2412",
  "source": "foil.tools",
  "units": { "Re": "dimensionless", "alpha": "degrees", "CL": "dimensionless", "CD": "dimensionless", "CM": "dimensionless" },
  "polars": [
    { "Re": 500000, "Ncrit": 9, "alpha": 0.0, "CL": 0.234, "CD": 0.00634, "CM": -0.0521 },
    { "Re": 500000, "Ncrit": 9, "alpha": 0.5, "CL": 0.289, "CD": 0.00628, "CM": -0.0522 },
    ...
  ]
}

GET/api/v1/polars/search

Rank airfoils by drag at a target operating point. Finds the closest available Reynolds bucket per airfoil, interpolates to the exact target CL in the pre-stall region, and returns matches sorted by ascending CD.

Parameters

Name	In	Required	Description
cl	query	Yes	Target lift coefficient, e.g. 0.6.
re	query	Yes	Target Reynolds number, e.g. 500000.
re_tol	query	No	Fractional Re tolerance for bucket matching (default 0.10 = ±10%).
max_cd	query	No	Discard results with CD above this threshold.
alpha_max	query	No	Discard results where the interpolated alpha exceeds this value (degrees).
family	query	No	Filter to a specific airfoil family, e.g. "Eppler".
limit	query	No	Maximum number of results to return (default 20, max 100).

Example

Request

curl "https://foil.tools/api/v1/polars/search?cl=0.6&re=500000&max_cd=0.012&limit=5"

Response

{
  "query": { "cl": 0.6, "re": 500000, "re_tol": 0.1, "max_cd": 0.012 },
  "count": 5,
  "results": [
    {
      "airfoil": "e387",
      "re_used": 500000,
      "alpha": 3.21,
      "CL": 0.6,
      "CD": 0.00681,
      "CM": -0.0831
    },
    ...
  ]
}

Status Codes

Code	Description
200	Success
404	Airfoil not found
429	Rate limit exceeded (60 requests/hour)
500	Internal server error

CORS

All /api/v1/* endpoints support cross-origin requests. The API returns Access-Control-Allow-Origin: * so you can call it directly from browser-based applications.