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Orbital speed at altitude calculator

Find the speed needed to stay in a circular orbit at a set height: 400,000 m above Earth's 6,371,000 m radius takes 7,672.598648 m/s. Enter altitude and radius, and the distance from the centre is added for you. Free in your browser.

  • Free
  • Runs in your browser
  • No sign-up
  • Your data stays on your device
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If you enter
Body radius
6,371,000
Altitude
400,000
Mu
398,600,441,800,000
You get
Total radius
6,771,000
Orbital speed
7,672.598648

Circular orbital speed at a stated altitude is the tangential speed a satellite needs to stay on a closed circular path above a spherical central body under Newtonian two-body gravity. Mission concept tools, classroom problems, and early LEO sketches often quote altitude above the surface rather than total radius from the centre, so the natural inputs are body radius R, altitude h, and the body’s standard gravitational parameter μ equals GM.

What orbital speed at altitude means and which inputs to send

Under inverse-square gravity and the circular two-body idealization, a satellite at constant distance from a central mass has constant tangential speed. Balancing gravitational acceleration μ over r squared with centripetal acceleration v squared over r yields v equals the square root of μ over r. When the design brief or textbook gives altitude above the surface instead of centre-to-satellite distance, set r equal to body radius plus altitude before taking the square root.

Altitude may be zero for a theoretical surface-grazing circular path when R is positive; negative altitudes that drive R plus h to zero or below fail. Send required field mu as the standard gravitational parameter in length cubed over time squared—for Earth about 3.986004418 times ten to the fourteenth in SI—so you do not need separate mass and G. All three fields are required and must be finite.

Classroom use and practical limits

Call the free in-browser orbital speed at altitude calculator for homework checks, lecture demos, and quick LEO or MEO concept verification without installing Orekit, GMAT, or a local MATLAB toolbox. Typical classroom examples include low Earth orbit near four hundred kilometres altitude with Earth radius and Earth μ, medium Earth orbits for GNSS-class altitudes, and simplified lunar or Mars circular paths with the matching body radius and gravitational parameter—always with consistent units.

Extremely large or tiny magnitudes are bounded for isolate safety; stay within the published numeric range for reliable results. Unlike calculators that take centre-to-satellite radius alone, this landing targets the search intent of speed at a stated altitude above the surface, which is how many problem sets and mission briefs phrase the question.

LEO and MEO concept sketches

Early mission tools that start from altitude above Earth or another body convert R, h, and μ into circular speed without reimplementing sqrt(μ/(R+h)) in every language.

What is mu and what units should I use?

mu is the standard gravitational parameter GM of the central body.

Is the orbital speed at altitude calculator free?

The browser tool runs free on your device.

How fast must a satellite fly 400,000 m above Earth?

About 7,672.598648 metres per second. With Earth's radius of 6,371,000 m the orbit is 6,771,000 m from the centre, and that distance sets the circular speed.

Why does the calculator need the body's radius?

Altitude is measured from the surface, but the speed depends on the distance from the centre. The calculator adds the radius and the altitude before working out the speed.

Does a higher orbit need more or less speed?

Less. Circular speed falls with the square root of the distance from the centre, so a satellite higher up moves more slowly than one skimming low over the surface.

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.

POSThttps://api.kit.forhosting.com/astro/orbital-speed-at-altitude

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.

curl -X POST https://api.kit.forhosting.com/astro/orbital-speed-at-altitude \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"body_radius":6371000,"altitude":400000,"mu":398600441800000}'
{
  "body_radius": 6371000,
  "altitude": 400000,
  "mu": 398600441800000
}
{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "astro.orbital_speed_at_altitude",
  "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.

Per request$0.002

Published price — no tokens, no invented credits. A failed task is never charged.

HTTPCodeMeaning
401unauthorizedMissing or invalid API key.
402insufficient_balanceYour balance doesn't cover the task price.
404unknown_typeThat task type doesn't exist.
429rate_limitedToo many requests. Use the webhook instead of polling.

This orbital speed at altitude calculator forms the total path radius r equals R plus h, evaluates v equals the square root of μ over r, and returns structured JSON that homework checkers and lightweight pipelines can pin in continuous integration. Non-positive total radius is rejected with a clear invalid_input error because the formula divides by r and a vanishing or inverted geometry is not a physical circular orbit.

What orbital speed at altitude means and which inputs to send

Send required field body_radius as a finite number or numeric string for the mean or equatorial radius of the body—for Earth about 6.371 times ten to the sixth metres—and required field altitude as the height above that surface in the same length units. Aliases R, radius, and planet_radius map to body_radius; h, height, and altitude_m map to altitude; gravitational_parameter, GM, and mu_body map to mu. Units are your responsibility: with metres and SI μ, orbital_speed is in metres per second. The path is pure floating-point arithmetic with no network, no random seed, and no wall clock, so identical inputs always produce identical JSON.

Reading the response fields, errors, and unit consistency

On success the response echoes body_radius, altitude, and mu, then reports total_radius as R plus h and orbital_speed as the circular speed magnitude. The formula field is always the string v equals sqrt of mu over open parenthesis R plus h close parenthesis, and method is always circular_orbital_speed_at_altitude so clients can branch without sniffing shapes. Missing body_radius, missing altitude, missing mu, non-finite values, non-positive mu, and non-positive total radius all fail with invalid_input and are not charged after the engine rejects the request. The product contract for this capability is explicit: when R plus h is not strictly positive, the solve aborts with a message that names total_radius and the sum that failed. That covers zero radius, inverted geometry from a large negative altitude, and other non-physical paths. Use orbital_speed alone when a dashboard only needs the speed number; keep total_radius and formula when documenting the step for students or when logging which algorithm produced a mission sketch. Pair this endpoint with orbital period tools when the next question is how long one revolution takes at the same altitude, remembering that period scales with r to the three-halves power while speed falls as one over the square root of r.

API usage, pricing, classroom workflows, and practical limits

Send a JSON body with required body_radius, altitude, and mu. Use the prepaid API when a tutoring platform, coding-assessment sandbox, curriculum generator, or early mission-design pipeline needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance after rejection. Authors shipping SDKs can map orbital_speed into tables that compare circular speeds across altitudes, teaching how speed falls as altitude grows while period lengthens—a companion concept you may compute separately when building multi-step lesson flows.

Homework and exam verification

Students and graders compute circular orbital speed for given body radius, altitude, and μ, compare against textbook answers, and get a clear invalid_input error when total radius is non-positive.

Tutoring and curriculum generators

Lesson builders produce worked altitude-based orbital-speed examples with structured JSON for flashcards, step sheets, and auto-graded drills without embedding a full astrodynamics library.

How do I calculate orbital speed at a given altitude?

Send JSON with body_radius (R), altitude (h), and mu (μ) as finite numbers. The response includes orbital_speed equal to sqrt(μ/(R+h)), plus total_radius and the formula label.

What happens if total radius is non-positive?

The request fails with invalid_input. When body_radius plus altitude is zero or negative, the circular-orbit formula is not defined and the solve is rejected without billing.

Is altitude the same as orbital radius?

No. Altitude is height above the surface. Total orbital radius from the centre is body_radius plus altitude. This calculator forms that sum for you.

Read the full KIT documentation →