Astronomy Surface Gravity

A planetary/stellar surface-g KPI. Distinct from Physics weight (mg) on Earth-g assumptions.

g = 6.6743×10⁻¹¹ × M ÷ R² (SI).

Tip: Keep “Mass M (kg)” and “Radius R (m)” on the same basis (units, period, and definition) before you calculate.

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Surface gravity for a spherical body is G times mass divided by radius squared.

Enter mass (kg) and radius (m). Uses G = 6.6743×10⁻¹¹.

Body mass in kilograms
Body radius in meters

Surface Gravity

Understanding Astronomy Surface Gravity

How we calculate. g = 6.6743×10⁻¹¹ × M ÷ R² (SI). See our methodology and accuracy policy .

Real-world scenario: A typical Astronomy Surface Gravity case uses mass m (kg) 5.97e24 and radius r (m) 6.37e6. Enter the same figures below to reproduce the worked path.

What is Astronomy Surface Gravity?

A planetary/stellar surface-g KPI. Distinct from Physics weight (mg) on Earth-g assumptions.

  • SI units (kg, m)
  • Spherical teaching model
  • G fixed on this page

The Formula

Surface Gravity
g = G M ÷ R²

Worked Example

Scenario: M = 5.97×10²⁴ kg; R = 6.37×10⁶ m.
Step 1: R² ≈ 4.0577×10¹³
Step 2: GM/R² ≈ 9.82
Answer: Surface gravity is approximately 9.82 m/s².

Common Use Cases

  • Homework: planet g
  • Study: pair with escape velocity
  • Lab: SI drills

Pro Tips

  • Convert km → m
  • Don’t use Earth-g Physics weight for other worlds
  • Pair with escape tool

Limitations: Astronomy Surface Gravity results are educational astronomy study aids—not navigation, mission planning, or professional observing advice. Confirm constants and units with your textbook or instructor.

Common mistakes

  • Swapping part and whole: The denominator must be the full total, not a subset.
  • Rounding too early: Carry extra decimal places through multi-step work before rounding the final percent.
  • Mixing percent and decimal forms: Enter rates in the format the calculator labels expect.

The worked example for astronomy surface gravity was verified with the calculator form on this page—enter the same values to confirm the result.

When to use this calculator

  • Use this page when your wording matches astronomy surface gravity and the form labels on screen.
  • Use percent of a number for “what is X% of Y?” problems.
  • Use number is what percent when you know part and whole and need the percent.

Still unsure about astronomy surface gravity? Start with the quick answer above, then open the linked calculator that matches your wording.

Comparison: when to use each method

Use this table to pick the right percent workflow before you calculate.

ScenarioWhen to use
Percent of a numberFinding a part of a whole (tax, tip, score)
Percent changeComparing old vs new values

Frequently Asked Questions

How do I use this astronomy surface gravity calculator?

For astronomy surface gravity, enter the values labeled on the form, then press Calculate. Compare the result to the worked example on this page.

What formula does this page use?

See the quick answer and formula box above for astronomy surface gravity—the same percentage calculator expression is applied to your inputs.

What if my result looks wrong?

When checking astronomy surface gravity, re-check part vs whole (or rate vs base), rounding, and whether percents were entered as 25 rather than 0.25 when the form expects percents.

Authoritative References

For astronomy study concepts, consult:

  • OpenStax Astronomy — free textbook reference
  • NASA — mission and outreach context
  • IAU — astronomical constants and naming