Calculate mass, force, or acceleration using Newton's Second Law: F = m × a.
| Formula | Expression |
|---|---|
| Force | F = m × a |
| Mass | m = F / a |
| Acceleration | a = F / m |
Enter values to calculate.
Our free mass calculator uses Newton's Second Law of Motion to solve for mass, force, or acceleration, whichever value you're missing, given the other two. It's a handy tool for physics students and anyone working through mechanics problems involving forces and motion.
Newton's Second Law: Force (F) = Mass (m) × Acceleration (a)
Rearranged to solve for mass: m = F ÷ a. Rearranged to solve for acceleration: a = F ÷ m.
Force is measured in newtons (N) in the SI system, where 1 newton equals the force needed to accelerate 1 kilogram at 1 meter per second squared. This calculator also supports common alternate units like pounds-force (lbf), kilonewtons, and standard gravity (g) for acceleration.
Mass is the amount of matter in an object and stays constant everywhere. Weight is actually a force, the result of gravity acting on mass (W = m × g), so this calculator's "force" mode can represent weight when acceleration is set to standard gravity (9.81 m/s²).
In the SI system, force is measured in newtons (N). One newton is the force required to accelerate a 1 kilogram mass at a rate of 1 meter per second squared. Common alternate units include pounds-force (lbf) and dynes.
Enter an object's mass and its weight (force) in the Force field, then solve for acceleration, this returns the local gravitational acceleration, which is 9.81 m/s² on Earth's surface.
F = m × a assumes mass doesn't change during the motion. For systems where mass changes over time, like a rocket burning fuel, a more general form of Newton's Second Law involving momentum (F = dp/dt) is required instead.
Kilograms are the standard SI unit of mass used worldwide in science and everyday life. Slugs are a less common imperial unit of mass, primarily used in US engineering and aerospace calculations, where 1 slug equals roughly 14.59 kilograms.