Weight Calculator

What is Weight in Physics?

Weight is the force exerted by gravity on an object. Unlike mass, which is a measure of the amount of matter in an object, weight depends on the gravitational field strength. It is calculated using the formula W = mg, where W is weight, m is mass, and g is the acceleration due to gravity. On Earth, gravity is approximately 9.81 m/s².

How to Use This Calculator

Select which variable you want to calculate: weight (W), mass (m), or gravity (g). Enter the known values with their units, and the calculator will automatically compute the result with step-by-step solutions. The tool supports multiple units for weight (newtons, dynes, pound-force, etc.), mass (kg, g, lb, oz), and gravity (m/s², ft/s², etc.). You can also use the planetary gravity reference table to find gravity values for different celestial bodies.

The Weight Formula

W = m × g

Derived Formulas

To find mass: m = W / g

To find gravity: g = W / m

Example Calculation

What is the weight of a 75 kg person on Earth?

W = 75 kg × 9.81 m/s²

W = 735.75 N

The person weighs approximately 735.75 newtons on Earth. On the Moon, the same person would weigh only about 121.5 N because the Moon's gravity is 1.62 m/s².

Frequently Asked Questions

What is the difference between weight and mass?

Mass is the amount of matter in an object and remains constant regardless of location. Weight is the force of gravity on an object and changes depending on the gravitational field. Mass is measured in kilograms (kg), while weight is measured in newtons (N). An astronaut has the same mass on Earth and the Moon, but weighs about one-sixth as much on the Moon.

What is standard gravity on Earth?

Standard gravity on Earth (g) is approximately 9.80665 m/s² (often rounded to 9.81 m/s² for calculations). This value varies slightly depending on latitude, altitude, and local geological features. The standard value of 1 gn = 9.80665 m/s² is used as the reference for many engineering and physics calculations.

What weight units does this calculator support?

The calculator supports newtons (N), dynes (dyn), kilogram-force (kgf), kilonewtons (kN), meganewtons (MN), giganewtons (GN), kips (kip), pound-force (lbf), ounce-force (ozf), and poundals (pdl). All conversions are performed automatically based on SI standards.

How does gravity vary on different planets?

Gravity varies significantly across celestial bodies: the Sun (274 m/s²), Mercury (3.70 m/s²), Venus (8.87 m/s²), Earth (9.81 m/s²), Mars (3.71 m/s²), Jupiter (24.9 m/s²), Saturn (10.44 m/s²), Uranus (8.87 m/s²), Neptune (11.15 m/s²), and Pluto (0.58 m/s²). The calculator includes a planetary gravity reference table for easy access to these values.

Where is weight calculation used in real-world applications?

Weight calculations are essential in aerospace engineering (calculating payload and thrust requirements), civil engineering (designing structures to support gravitational loads), sports science (analyzing athlete performance under different gravity conditions), physics education (understanding forces and motion), and space exploration (planning missions to other planets and moons).

Is weight the same as the force in F = ma?

Yes, weight is a specific case of Newton's second law (F = ma) where the acceleration is gravity (g). So W = mg is just F = ma with a = g. This means weight is truly a force, and the standard unit of weight in physics is the newton (N), not the kilogram.

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