Banked curve calculator
A curve with a 50 m radius taken at 20 m/s needs a bank of 39.1970508975 degrees if no friction is to help: the calculator solves tan θ = v²/(r·g) and gives the angle in degrees and radians. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Radius
- 50
- Speed
- 20
- G
- 9.81
- Tan theta
- 0.8154943935
- Angle rad
- 0.6841175952
- Angle deg
- 39.1970508975
A banked curve lets a vehicle negotiate a circular turn without relying on tire friction when the roadway is tilted at the ideal angle for a chosen design speed. In the classic frictionless model the horizontal component of the normal force supplies the centripetal requirement while the vertical component balances weight, which collapses to the compact relation tan of theta equals speed squared over radius times g. Students checking homework, teachers writing answer keys, highway and track designers sanity-checking a design bank, and simulation authors wiring circular-path constraints all need the same two primary inputs—radius and speed—plus an optional gravity constant, and one clear angle they can trust.
What the ideal banked-curve angle means and which quantities you must send
In introductory classical mechanics, a car of any mass travels at constant speed v on a level circular path of radius r only if a net horizontal force of magnitude m v squared over r points toward the center. On a banked roadway of angle theta with no friction, the normal force N is perpendicular to the surface: N cos theta balances mg while N sin theta supplies the centripetal force, so dividing the two equilibrium equations eliminates mass and yields tan theta equals v squared over r g.
That identity is the backbone of banked-curve problem sets, highway design speed checks, velodrome and racetrack tilt estimates, and countless engineering order-of-magnitude sketches: what bank angle keeps a vehicle on the design circle at the posted speed without needing lateral friction. Search intent clusters around phrases such as banked curve calculator, banking angle calculator, frictionless banked turn, ideal bank angle from radius and speed, and tan theta equals v squared over r g.
People want a numeric angle they can check against a worksheet, embed in a simulation, or feed into a larger pipeline—not only a reminder that the formula exists. Units stay consistent with whatever length, speed, and gravity basis you chose: metres with metres per second and metres per second squared yield a pure angle; mass never enters the ideal frictionless result.
Practical use, limits, pricing, and delivery channels
Use the browser tool when you want an immediate ideal bank-angle check while grading homework, verifying a lab circular-track demo, sanity-checking a game racetrack tilt, or sketching highway design bank for a known radius and posted speed. Choose units consistently—if radius is in metres, speed in metres per second, and g in metres per second squared, the angle is ready for free-body diagrams and design notes without further conversion.
There is no language model, no external physics service, and no randomness, so the capacity is safe to pin in continuous-integration checks and reproducible lesson materials. Pair with a centripetal-force tool when you also need the force magnitude at the same speed and radius, remembering that force still depends on mass while the ideal bank angle does not.
What you can do with it
Homework and lab banked-curve drills
Students and graders confirm the ideal frictionless bank angle for given radius and speed, with clear rejection when radius is zero or speed is negative.
Track, highway, and sim design checks
Quick structured angles for road bank, velodrome tilt, or game racetrack slope estimates without standing up a full vehicle-dynamics stack.
FAQ
What happens if radius is zero?
Zero radius is invalid for a banked circular path and would divide by zero in tan(θ)=v²/(r g); validation failures are not charged.
Does mass affect the ideal bank angle?
No. In the frictionless model mass cancels, so only radius, speed, and g are needed.
Is the banked curve calculator free?
The browser tool runs free on your device.
Does this include friction or maximum safe speed?
No. This capacity returns only the ideal frictionless bank angle. Friction-limited min/max speeds and μ_s models are a different product intent.
What units should I use for radius, speed and gravity?
Any coherent set, such as metres, metres per second and metres per second squared. The angle itself has no unit, so it comes out the same in any consistent system; the calculator does not convert units for you.
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/mech/banked-curve \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"radius":50,"speed":20}'const res = await fetch("https://api.kit.forhosting.com/mech/banked-curve", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"radius": 50,
"speed": 20
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/mech/banked-curve",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"radius": 50,
"speed": 20
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/mech/banked-curve", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"radius":50,"speed":20}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"radius":50,"speed":20}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/mech/banked-curve", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"radius": 50,
"speed": 20
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "mech.banked_curve",
"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
This capacity accepts those fields as finite numbers, rejects zero or non-positive radius with a clear invalid_input error so division by zero is never silent, rejects negative speed and non-positive g, and returns tan of theta with the bank angle in both radians and degrees as structured JSON labeled with formula and method.
What the ideal banked-curve angle means and which quantities you must send
Delivering radius, speed, g, tan_theta, angle_rad, angle_deg, formula, and method as JSON makes the result easy to paste into notes, diff in automated tests, or reuse across languages without reimplementing arctangent arithmetic.
How this calculator validates input and applies θ = arctan(v² / (r g))
Numeric strings that parse to finite numbers are accepted so forms and CSV-style pipelines can pass values without an extra cast. Speed must be non-negative because the product treats it as the magnitude of the design tangential velocity; negative speed is rejected rather than silently squared into a positive tan theta. When g is omitted the engine uses nine point eight one in SI units; when provided it must be strictly positive. There is no friction coefficient, no maximum or minimum safe speed band, no mass field, and no unit conversion; this is the ideal frictionless bank for the two known kinematic quantities. Send a JSON body with required fields radius and speed, and optional g for gravitational acceleration. Every required field must be finite: missing fields, empty strings, non-numeric text, NaN, and Infinity all fail immediately with invalid_input before any result is returned, and failed validation is not charged. Radius must be strictly positive: a zero radius is explicitly invalid for circular motion and would divide by zero in the formula, so the engine returns invalid_input with a message that names radius and the division-by-zero risk in tan theta equals v squared over r g. After validation, tan_theta is computed as speed times speed divided by radius times g, angle_rad is the arctangent of that ratio, and angle_deg converts radians to degrees by multiplying by one hundred eighty over pi. Results are rounded to a stable decimal precision so the same input always yields the same JSON across JavaScript engines. Aliases r, v or velocity, and gravity are accepted. The same pure function powers the free in-browser tool and the API path.
Practical use, limits, pricing, and delivery channels
Each successful request is one billable item at $0.002; failed validation does not consume balance. Results are fully deterministic: the same radius, speed, and g always yield the same tan_theta, angles, and formula label. Wire the endpoint into mechanics drills, contest answer checkers, highway-design worksheets, or preprocessing steps where you already prefer explicit domain errors—such as rejecting a zero radius—over opaque black-box widgets that cannot explain why a bad input was refused.
Integration use cases
Deterministic fixtures for physics tests
Pipelines that seed unit tests or interactive mechanics demos can call a pure θ=arctan(v²/(r g)) oracle instead of reimplementing banked-curve math in every language.
Technical questions
How do I calculate the ideal banking angle for a frictionless curve?
Send JSON with radius and speed (for example radius: 50, speed: 20). The response includes tan_theta, angle_rad, and angle_deg using θ = arctan(v²/(r g)). Optional g defaults to 9.81.