Weight Calculator
Convert mass to weight under Earth or any other gravity, and between units.
Inputs
Weight (Newtons)
686.4655N
Weight (kgf)
70.0000kgf
Weight (lbf)
154.3236lbf
Mass
70.0000kg
Gravity Body
Earth
g
9.80665m/s²
Step by step
Mass in kg
= 70 kg
Gravitational acceleration on Earth
= 9.80665 m/s²
Weight = mass × g
70 kg × 9.80665 m/s²
= 686.4655 N
In kilogram-force (kgf)
686.4655 N ÷ 9.80665
= 70 kgf
In pound-force (lbf)
686.4655 N ÷ 4.44822
= 154.3236 lbf
How it works
Weight is the gravitational force on a mass: W = m × g. On Earth, g ≈ 9.807 m/s² (varies slightly with latitude and altitude). On the Moon g ≈ 1.62 m/s², so a 70 kg person weighs about 686 N on Earth but only 113 N on the Moon — though their mass remains 70 kg everywhere.
Formula
Weight
Weight (N) = Mass (kg) × Gravitational acceleration (m/s²)
- W
- Weight in Newtons
- m
- Mass in kilograms
- g
- Gravitational acceleration in m/s²
Frequently Asked Questions
What is my weight on Mars?
Mars has about 38% of Earth's surface gravity (3.72 m/s² vs 9.81 m/s²). A 70 kg person would weigh about 260 N on Mars compared to 686 N on Earth — less than 40% of their Earth weight.
What is the difference between mass and weight?
Mass (kilograms) measures the amount of matter — it's the same everywhere. Weight (Newtons) is the gravitational force on that mass, which varies with the local gravitational acceleration g.
Why does a bathroom scale show kilograms, not Newtons?
Bathroom scales display mass (kilograms) or kilogram-force (kgf), not scientific Newtons. Because g is approximately constant on Earth's surface, scales are calibrated to divide the force reading by 9.807 and show kg. In physics, weight is always a force in Newtons.
Why is the Sun's gravity so high?
The Sun's surface gravity is 274 m/s² — about 28 times Earth's — because of its enormous mass (333,000 × Earth). However, the Sun has no solid surface; spacecraft encounter the Sun's gravity from orbit, not its surface.