Why does orbital velocity decrease with altitude?

Gravity weakens with distance (1/r²), so less centripetal acceleration is needed at higher altitudes. Since v = √(GM/r), velocity decreases as the square root of the increasing orbital radius.

What is the difference between orbital and escape velocity?

Orbital velocity maintains a circular orbit; escape velocity is the speed needed to leave the gravitational field entirely. Escape velocity is always √2 ≈ 1.414 times the circular orbital velocity at the same altitude.

The ISS orbits at about 7.67 km/s (27,600 km/h or 17,150 mph) at an altitude of approximately 400 km. It completes one orbit every ~92 minutes.

What altitude is geostationary orbit?

Geostationary orbit (GEO) is at 35,786 km altitude, where the orbital period matches Earth rotation (23 h 56 m). The satellite appears stationary relative to the ground.

Does satellite mass affect orbital velocity?

No. Orbital velocity depends only on the central body mass and the orbital radius. All objects at the same altitude orbit at the same speed regardless of their mass — this is why astronauts experience weightlessness.

Can you orbit at any altitude?

In theory, yes, but practically the orbit must be above the atmosphere (>160 km for Earth) and below gravitational influence limits. Low orbits experience atmospheric drag and decay without station-keeping.

Orbital Velocity Calculator

Calculate circular orbital velocity, period, and escape velocity for any altitude around Earth, Mars, Moon, Jupiter, Sun, or a custom body. Includes orbit types reference.

Central Body

Orbital Altitude

Satellite Mass

Orbital Velocity

7.672 km/s

7,672 m/s

Orbital Period

1.54 h

5,545 s

Escape Velocity

10.850 km/s

1.414× orbital

Gravitational Accel

8.6936 m/s²

0.8862 g

Surface Gravity

9.820 m/s²

1.001 g

Orbital Radius

6,771 km

1.06 × body radius

Specific Orbital Energy

-29.43 MJ/kg

Total E per unit mass

Kinetic Energy

1.24e+4 GJ

½mv²

Velocity Comparison

Orbital v

7.67 km/s

Escape v

10.85 km/s

Δv to escape

3.18 km/s

Common Orbit Types

Orbit Type	Altitude	Period	Speed	Typical Use
LEO (Low Earth)	200–2,000 km	88–127 min	6.9–7.8 km/s	ISS, Hubble, imagery
MEO	2,000–35,786 km	2–24 h	3.1–6.9 km/s	GPS, Galileo
GEO	35,786 km	24 h	3.07 km/s	Communications, weather
HEO	Variable (Molniya)	12 h	Variable	High-latitude comms
Lunar	384,400 km	27.3 d	1.02 km/s	Moon

Planning notes, formulas, and examples

About the Orbital Velocity Calculator

For a circular orbit, there is one speed where gravity supplies exactly the centripetal force needed to hold altitude: v = sqrt(GM/r). That orbital speed, along with the period and escape velocity, is the core of basic astrodynamics.

This calculator computes circular-orbit parameters for Earth, Moon, Mars, Jupiter, the Sun, or a custom body. Enter the central body and altitude to obtain orbital speed, period, escape speed, gravitational acceleration, and orbital energy.

Presets for the ISS, GPS, geostationary orbit, and lunar orbit make it easier to compare common mission profiles and see how altitude changes the required speed.

When This Page Helps

Orbital mechanics is easy to state and easy to misapply once altitude, body radius, and escape speed are involved. A calculator that shows orbital speed, period, and escape velocity together makes it simpler to compare common orbit regimes.

That is useful when you are checking a satellite concept, comparing planets or moons, or estimating how far a circular orbit sits from escape conditions.

How to Use the Inputs

Select a central body (Earth, Moon, Mars, Jupiter, Sun, or custom).
Choose a preset orbit or enter altitude in km manually.
Enter the satellite mass for energy calculations.
Read orbital velocity, period, escape velocity, and energy.
Use the velocity comparison chart to see how close orbital speed is to escape speed.
Check the orbit types table for context on LEO, MEO, GEO, and beyond.

Formula used

Orbital Velocity (circular):
  v = √(GM / r)

Orbital Period:
  T = 2πr / v

Escape Velocity:
  v_esc = √(2GM / r) = v_orb × √2

Gravitational Acceleration at orbit:
  a = GM / r²

Specific Orbital Energy:
  ε = −GM / (2r)

Where:
  G = 6.674 × 10⁻¹¹ N·m²/kg²
  M = central body mass (kg)
  r = R_body + altitude (m)
  R_body = body radius (m)

Example Calculation

Result: v ≈ 7.67 km/s, T ≈ 92.4 min

The ISS orbits at 400 km altitude (r = 6,771 km from Earth center). At this radius, v = √(GM/r) = 7,672 m/s. The period is 2πr/v ≈ 5,540 s ≈ 92 min. Escape velocity is 10.85 km/s — about 41% higher than orbital speed.

Tips & Best Practices

Escape velocity is always √2 × orbital velocity at the same altitude.
The orbital period at GEO is ~24 hours — this is why GEO satellites appear stationary.
For quick estimates: LEO speed ≈ 7.8 km/s, GEO speed ≈ 3.1 km/s.
Orbital energy is negative (bound orbit). Zero total energy means escape.
The Moon orbits at ~1.02 km/s — much slower than LEO satellites because it is much farther away.

Kepler's Laws and Circular Orbits

Kepler's third law relates orbital period to semi-major axis: T² ∝ a³. For circular orbits (a = r), this simplifies to T = 2π√(r³/GM). This law allows calculating the orbit of any body if you know the central mass. Newton showed that Kepler's empirical laws follow directly from universal gravitation.

Delta-v and Orbital Maneuvers

Changing from one orbit to another requires a velocity change (delta-v). The most fuel-efficient way to transfer between two circular orbits is the Hohmann transfer — two engine burns separated by half an elliptical orbit. The delta-v from LEO to GEO is about 3.9 km/s, which is why geostationary satellites need such large upper stages.

Atmospheric Drag and Orbital Decay

Satellites in low Earth orbit experience atmospheric drag that gradually reduces their altitude and speed (paradoxically, they speed up as they descend to orbits where orbital velocity is higher). The ISS requires periodic reboosts (about 7 km/year altitude loss without correction). Above ~1,000 km, drag is negligible and orbits are stable for centuries.

Sources & Methodology

Last updated: March 7, 2026

Frequently Asked Questions

Gravity weakens with distance (1/r²), so less centripetal acceleration is needed at higher altitudes. Since v = √(GM/r), velocity decreases as the square root of the increasing orbital radius.