The force calculator applies Newton's second law: Force = Mass × Acceleration (F = ma). Solve for any of the three variables — force, mass, or acceleration — by entering the other two. Supports metric (Newtons, kg) and imperial (pound-force, lb) units.
Force Calculator (F = ma)
How to Use the Force Calculator
This force calculator implements Newton's second law of motion: F = ma. It solves for any of the three variables — force, mass, or acceleration — when the other two are known.
Step 1: Choose What to Solve For
Select Force (F), Mass (m), or Acceleration (a) from the three option buttons. The selected variable will be calculated from the other two inputs.
Step 2: Select Units
Metric uses Newtons (N) for force and kg for mass. Imperial uses pound-force (lbf) and pounds (lb). Acceleration uses m/s² in metric and ft/s² in imperial.
Step 3: Enter Known Values and Calculate
Enter the two known values and click Calculate. Example: a 5 kg object with acceleration 3 m/s² has Force = 5 × 3 = 15 N.
Common Examples
Weight calculation: A 70 kg person on Earth experiences gravitational force = 70 × 9.81 = 686.7 N (about 154 lbf).
Car braking: A 1,200 kg car decelerating at 8 m/s² requires a braking force of 9,600 N.
Rocket thrust: If a 500 kg rocket achieves 30 m/s² acceleration, thrust = 15,000 N.
Frequently Asked Questions
What is Newton's second law (F = ma)?
Newton's second law states that Force equals mass times acceleration (F = ma). Force is measured in Newtons (N), mass in kilograms (kg), and acceleration in m/s². A 2 kg object accelerating at 5 m/s² experiences a net force of 10 N.
What is the difference between mass and weight?
Mass is a measure of how much matter an object contains (kg), while weight is the gravitational force acting on that mass (N or lbf). On Earth, weight = mass × 9.81 m/s². A 70 kg person weighs 686.7 N (or about 154.3 lbf) on Earth.
Is this calculator free?
Yes, completely free with no signup required. All calculations happen in your browser.
Is my data private?
Yes. All calculations run locally in your browser. Nothing is transmitted or stored.
What units does this support?
Metric: Newtons (N) for force and kg for mass. Imperial: pound-force (lbf) and pounds (lb). Acceleration is in m/s² or ft/s² depending on the unit mode selected.