Force Calculator

Calculate force from mass and acceleration with Newton's second law, plus weight and pressure.

By Konstantin Iakovlev · Updated September 2026 · Source: Khan Academy

Force

98.10 N

Weight

98.10 N

F = m x a

Force98.10 N
Weight (mg)98.10 N
Pressure (F/A)196.20 Pa

Use the Force Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only. Results are estimates based on the information you provide and the assumptions described on this page.

How It Works

Newton's Second Law of Motion ties force, mass, and acceleration together, and this tool computes the force from a mass and an acceleration. It also shows the object's weight on Earth and, if you give a contact area, the pressure that force exerts. The relationship matters well beyond the classroom, underpinning work in robotics, aerospace engineering, and sports analytics.

The law is written F = ma, with F for force, m for mass, and a for acceleration. Enter the mass in kilograms and the acceleration in meters per second squared, and the calculator returns the force in newtons. It also reports weight as mass × 9.81 m/s^2 and pressure as force ÷ area in pascals. To find a mass or an acceleration instead, rearrange by hand: m = F/a or a = F/m.

Inputs need to share consistent units, because that is where results most often go wrong. The inputs are fixed in kilograms and meters per second squared, so convert pounds or feet per second squared first; a speed such as miles per hour is not an acceleration at all. One more point worth holding onto: force is a vector with both magnitude and direction, even though this calculator deals only with magnitude.

Example: Net Force on an Accelerating Cart

  1. 1 A 250 kg cart on a level track speeds up at 5 m/s². What net force is acting on it?
  2. 2 Enter mass 250 and acceleration 5. F = m × a = 250 kg × 5 m/s² = 1,250 N.
  3. 3 The calculator shows a force of 1,250.00 N. It also shows the cart's weight, 250 × 9.81 = 2,452.50 N, and a pressure line that divides the force by the Area field (0.5 m² by default: 1,250 / 0.5 = 2,500.00 Pa), which you can ignore here.
  4. 4 1,250 N is the net force. If friction and air drag also act on the cart, the push has to exceed 1,250 N by whatever those resist.

Source: Khan Academy · Last updated: September 2026

Frequently Asked Questions

What is Newton's second law of motion?
Newton's second law states that force equals mass times acceleration (F = ma). A net force of 1 newton accelerates a 1-kilogram mass at 1 meter per second squared. If multiple forces act on an object, the net force determines the acceleration.
What is the difference between mass and weight?
Mass is the amount of matter in an object (measured in kilograms) and is constant everywhere. Weight is the gravitational force on that mass (measured in newtons) and varies with gravity. On Earth, weight in newtons equals mass times 9.81 m/s2.
How do I convert between newtons and pounds-force?
One newton equals approximately 0.2248 pounds-force, and one pound-force equals 4.448 newtons. A 1-kilogram mass weighs 9.81 newtons or about 2.2 pounds on Earth.

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