What is circular orbital velocity?

Circular orbital velocity is the exact speed a spacecraft must maintain so that centripetal acceleration equals gravitational acceleration at that altitude. At the ISS orbit (~410 km), it is roughly 7.66 km/s (27,600 km/h). Fly faster and you spiral outward; fly slower and you spiral back toward Earth.

Why does orbital speed decrease with altitude?

Gravity weakens with distance (g ∝ 1/r²), so a satellite in a higher orbit needs less centripetal force and therefore less speed to stay in balance. However, the orbit's circumference is also larger, which is why the orbital period increases much faster than speed decreases.

What is the geostationary orbit altitude?

Geostationary orbit (GEO) sits at about 35,786 km above Earth's surface — an orbital radius of 42,164 km from Earth's center. At this altitude the orbital period exactly matches Earth's rotation period (23 h 56 min), so the satellite appears stationary over one point on the equator.

What is GM used in the calculation?

GM (the standard gravitational parameter for Earth) is 3.986004418 × 10¹⁴ m³/s². This product of the gravitational constant G and Earth's mass M is known to much higher precision than either G or M individually, so it is the preferred constant in astrodynamics.

Does this account for atmospheric drag?

No. The calculator gives the ideal Keplerian (drag-free) result. In low orbits below about 600 km, atmospheric drag is significant and a spacecraft must fire its engine periodically to maintain altitude. Drag effects require numerical propagation and are beyond a simple closed-form formula.

Can I use this for orbits around other planets?

This tool is calibrated for Earth (GM = 3.986 × 10¹⁴ m³/s², radius 6,371 km). The underlying formula v = √(GM_body / r) is universal, but you would need to substitute the target body's GM and radius. Future versions may add multi-body support.

Orbital Velocity Calculator

Enter an orbital radius or altitude to compute circular orbit velocity, orbital period, and gravitational acceleration at that orbit.

Orbit Parameters

Orbital Radius from Earth's Center

Must be ≥ 6,371 km (Earth's mean surface radius).

Common Orbit Presets

Orbital Results

Enter an orbital radius or altitude above to compute orbit parameters.

Orbit Regime Reference

Region	Altitude	Approx. Speed
LEO	160 – 2,000 km	7.8 – 6.9 km/s
MEO	2,000 – 35,786 km	6.9 – 3.07 km/s
GEO	35,786 km	3.07 km/s
HEO / GTO	> 35,786 km	< 3.07 km/s
Moon orbit	~384,400 km	~1.02 km/s

Summary

This calculator applies Newton's law of gravitation and the vis-viva equation to find the velocity required to maintain a stable circular orbit at any altitude above Earth. For a circular orbit at radius r from Earth's center, the orbital speed is v = √(GM/r), the period is T = 2π√(r³/GM), and gravitational acceleration is g = GM/r². Enter either the orbital radius measured from Earth's center, or the altitude above sea level, and the tool converts between them automatically.

How it works

Enter the orbital radius from Earth's center, or switch to altitude mode and enter height above sea level.
The calculator derives the complementary value using Earth's mean radius (6,371 km).
Orbital velocity is computed with v = √(GM/r), where GM = 3.986 × 10¹⁴ m³/s².
Orbital period follows from T = 2π√(r³/GM), converted to hours and minutes.
Gravitational acceleration at that orbit uses g = GM/r².
Results update live; use the preset buttons to jump to common orbits instantly.

Use cases

Estimate the speed and period of a satellite at any target altitude.
Verify delta-v requirements when designing a transfer orbit maneuver.
Compare LEO, MEO, and GEO parameters side by side.
Understand why geostationary satellites orbit at exactly 35,786 km altitude.
Calculate gravitational acceleration in orbit for microgravity mission planning.
Teach orbital mechanics and Kepler's third law in classroom settings.
Cross-check simulation outputs from orbital mechanics software.
Explore how orbital velocity drops as altitude increases.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu