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Mass Calculator

Calculate mass from force and acceleration or convert between mass units worldwide.

A mass calculator determines mass from force and acceleration using Newton's second law (F = ma), or converts between mass units.

Select what to solve for (force, mass, or acceleration), enter the known values with their units, and the calculator applies Newton's second law (F = ma).

Examples

Weight of a 70 kg person

F = 70 kg x 9.81 m/s² = 686.7 N (about 154.4 lbf). Weight is the force of gravity acting on mass.

Acceleration of a pushed cart

A 50 N force on a 10 kg cart: a = 50 / 10 = 5 m/s².

Frequently Asked Questions

What is the difference between mass and weight?
Mass is the quantity of matter (kg), constant regardless of location. Weight is the gravitational force on that mass (Newtons), which varies with location. On the Moon, your mass stays the same but your weight is about 1/6th of Earth.
What is a Newton?
A Newton (N) is the SI unit of force. It is the force required to accelerate a 1 kg mass by 1 m/s². 1 N is approximately the weight of a small apple (about 0.225 lbf).
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Quick Tips

  • •Earth's gravitational acceleration is approximately 9.81 m/s² (32.2 ft/s²).
  • •A slug is the imperial unit of mass: 1 slug = 14.59 kg.
  • •Force due to gravity (weight) = mass x g. This is why we often confuse mass and weight.

A mass calculator determines mass from force and acceleration using Newton's second law (F = ma), or converts between mass units.

How to Use This Calculator

Select what to solve for (force, mass, or acceleration), enter the known values with their units, and the calculator applies Newton's second law (F = ma).

Understanding the Formula

F = m x a (Newton's Second Law). Force (N) = Mass (kg) x Acceleration (m/s²). Rearranged: m = F/a, a = F/m. All units are converted to SI (N, kg, m/s²) internally.

Examples

Weight of a 70 kg person

F = 70 kg x 9.81 m/s² = 686.7 N (about 154.4 lbf). Weight is the force of gravity acting on mass.

Acceleration of a pushed cart

A 50 N force on a 10 kg cart: a = 50 / 10 = 5 m/s².

Frequently Asked Questions

What is the difference between mass and weight?

Mass is the quantity of matter (kg), constant regardless of location. Weight is the gravitational force on that mass (Newtons), which varies with location. On the Moon, your mass stays the same but your weight is about 1/6th of Earth.

What is a Newton?

A Newton (N) is the SI unit of force. It is the force required to accelerate a 1 kg mass by 1 m/s². 1 N is approximately the weight of a small apple (about 0.225 lbf).

Assumptions & Limitations

  • Assumes constant acceleration and no friction or air resistance.
  • Uses standard gravitational acceleration (9.81 m/s²) for weight calculations.
  • Does not account for relativistic effects at near-light speeds.