Wind-shear gradient calculator
10 knots at 50 ft and 35 knots at 2000 ft mean a shear of about 12.8 knots per 1000 ft, classed as strong. Add both wind directions and it also measures the vector shear that a direction change at constant speed would hide. Free in your browser.
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Run — free
Worked example
- Speed lower
- 10
- Speed upper
- 35
- Height lower
- 50
- Height upper
- 2,000
- Speed unit
- Kt
- Height unit
- Ft
- Speed lower kt
- 10
- Speed upper kt
- 35
- Height lower ft
- 50
- Height upper ft
- 2,000
Vertical wind shear is the change of wind speed or of the wind vector between two altitudes. Pilots, dispatchers, and meteorologists use that gradient to judge low-level turbulence and the chance that an aircraft will lose or gain airspeed on final approach. This wind-shear gradient calculator takes wind speeds at a lower and an upper station, converts them to knots and metres, and returns the bulk two-level gradient in knots per thousand feet, knots per hundred feet, metres per second per kilometre, and inverse seconds. When both meteorological directions are supplied, it also reports the vector shear that a heading change at constant speed would hide.
What vertical wind shear is and how the two-level gradient is computed
Vertical wind shear is the change of the horizontal wind with height. In aviation weather it is the quantity that turns a gusty surface report into a statement about whether the next two thousand feet of climb will feel smooth, choppy, or suddenly fast or slow. The bulk two-level form used in briefings is simple: the shear gradient equals the change in wind between an upper observation and a lower observation, divided by the thickness of that layer.
When you send only speeds, the change is the signed difference of upper minus lower, so a wind that strengthens with height is positive and a wind that weakens with height is negative. The magnitude of that change, divided by the height difference, is reported in several aviation and SI units at once: knots per one thousand feet for environmental and turbulence language, knots per one hundred feet for low-level wind-shear and approach language, metres per second per kilometre, and inverse seconds.
When you also send both wind directions, using the meteorological convention that direction is the compass point the wind blows from, the calculator converts each observation to eastward and northward components, takes the vector difference, and uses that magnitude as the primary shear for intensity and approach classes. Vector shear is the quantity that actually changes an aircraft's inertial wind on a short climb or descent; a one-hundred-eighty-degree direction shift at constant speed is a large shear even though the scalar speed difference is zero.
Heights must increase from the lower station to the upper station; equal or inverted heights are rejected rather than silently flipping the sign. Speeds must be finite and non-negative. This is a two-point planning identity, not a full wind profile, a lidar scan, or a substitute for a missed-approach decision.
Where a wind-shear gradient calculator earns its keep
Approach and landing briefings need a repeatable number when the ATIS, a PIREP, or a low-level wind-shear alert mentions a speed jump between the surface and a few hundred feet. Feeding those two winds and heights into one contract produces the knots-per-hundred-feet figure that FAA and ICAO language uses for significant low-level wind shear, together with a caution, warning, or severe approach class the instructor or dispatcher can put on a card.
Mountain-wave, rotor, and frontal-turbulence lessons use the same two-level gradient in knots per thousand feet so students can see why a twenty-knot speed change in two thousand feet is a different risk from the same change in two hundred feet. Failed validation does not consume balance. Keep requests small, pin the rounded gradients in tests, and you get a reproducible first-cut shear for briefings, LMS items, and edge workers without standing up a mesoscale model.
Always pair the number with the official forecast, aircraft category, and your own go-around criteria; this calculator is the two-level arithmetic, not a clearance to continue an unstable approach.
What you can do with it
Low-level turbulence and mountain-wave screens
Compare a valley floor wind with a ridge or sounding wind in knots per thousand feet to show students why layer thickness changes the turbulence story.
Dispatch and PIREP comparison
Batch two-level shears from ATIS, METARs, and PIREPs through one parse contract instead of maintaining a private UV spreadsheet at each base.
FAQ
How is the vertical wind-shear gradient computed?
Results are reported in kt/1000 ft, kt/100 ft, m/s per km, and inverse seconds. When both meteorological from-directions are sent, the primary shear is the vector magnitude √(Δu²+Δv²) / Δz.
Do I have to send wind directions?
Send both (0–360, meteorological from) to add vector shear.
What do the intensity classes mean?
Intensity uses the absolute primary shear in knots per 1000 ft: calm below 2, light 2–5, moderate 5–10, strong 10–20, severe 20 and above. It is a planning label, not a SIGMET.
What does a negative wind shear result mean?
It means the wind weakens with height. With speeds only, the change is the upper speed minus the lower one, so a wind that strengthens as you climb gives a positive result and one that dies off gives a negative result.
Why can strong shear over a thick layer show no approach hazard?
Because the two scales answer different questions. The intensity class looks at the gradient itself, while the approach class is meant for thin low-level layers. In the example, 12.8 knots per 1000 ft is strong, yet a 1950 ft layer is too thick to count as an approach hazard.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/travel/wind-shear-gradient \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"speed_lower":10,"speed_upper":35,"height_lower":50,"height_upper":2000}'const res = await fetch("https://api.kit.forhosting.com/travel/wind-shear-gradient", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"speed_lower": 10,
"speed_upper": 35,
"height_lower": 50,
"height_upper": 2000
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/travel/wind-shear-gradient",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"speed_lower": 10,
"speed_upper": 35,
"height_lower": 50,
"height_upper": 2000
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/travel/wind-shear-gradient", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"speed_lower":10,"speed_upper":35,"height_lower":50,"height_upper":2000}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"speed_lower":10,"speed_upper":35,"height_lower":50,"height_upper":2000}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/travel/wind-shear-gradient", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"speed_lower": 10,
"speed_upper": 35,
"height_lower": 50,
"height_upper": 2000
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "travel.wind_shear_gradient",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Missing, inverted, or non-physical inputs fail with invalid_input instead of inventing a gradient.
Input contract, units, response shape, and error behaviour
Speeds must be greater than or equal to zero. The upper height must be strictly greater than the lower height so the layer has a positive thickness. After conversion, speeds must stay at or below four hundred knots and heights must stay between minus two thousand and eighty thousand feet so a unit typo cannot produce a stratospheric nonsense gradient. When directions were supplied the response also includes the vector wind change and the vector gradients. Example: ten knots at fifty feet and thirty-five knots at two thousand feet yields a positive speed shear of about twelve point eight knots per thousand feet, classed as strong for environmental intensity and none for the thin-layer approach scale because the layer is thick. POST a JSON body with four required finite numbers: speed_lower and speed_upper, the wind speeds at the lower and upper stations, and height_lower and height_upper, the altitudes of those stations. Optional speed_unit is one of kt, m_s, km_h, or mph and defaults to knots, the aviation briefing unit. Optional height_unit is ft or m and defaults to feet. Optional direction_lower and direction_upper are meteorological from-directions in degrees from zero through three hundred sixty; send both or neither. If only one direction arrives the request fails, because a half vector is not a shear. Each numeric field may arrive as a JSON number or as a numeric string; aliases such as v1, v2, z1, z2, wind_lower, and alt_upper are accepted. Those validation failures return invalid_input and are not billed. On success the body echoes the cleaned inputs, reports both stations in knots and feet, the signed speed change, the layer thickness, the signed speed gradient, absolute gradients used for classification, SI gradients, shear_kind as speed or vector, intensity, approach_class, and approach_hazard, plus formula, method, and a short message.
Where a wind-shear gradient calculator earns its keep
Charter and aerial-work planners batch a morning line of destinations through one parse endpoint instead of re-deriving vector components in a private spreadsheet that drifts between bases.
Integration use cases
Approach and landing briefings
Turn a surface wind and a two-hundred-foot or tower wind into knots per hundred feet and an approach class before short final, so the brief matches the same number the API would return.
Technical questions
When is approach_hazard true?
When the absolute primary shear is at least 5 kt per 100 ft (approach_class warning or severe). That thin-layer scale matches low-level wind-shear language; a thick 2000 ft layer with the same total ΔV may stay none.
What does the wind-shear gradient calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.