Zerdly

Force, Mass & Acceleration Calculator

This tool applies Newton's second law of motion, F = m × a, where F is the net force in newtons (N), m is mass in kilograms (kg) and a is acceleration in metres per second squared (m/s²).

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How to use this calculator

Enter Values

Enter your values and press Calculate to see results.

How to use this calculator

  1. Fill in any two of the three fields — Force (N), Mass (kg) and Acceleration (m/s²) — and leave the one you want to find blank.
  2. Use consistent SI units: newtons for force, kilograms for mass, metres per second squared for acceleration.
  3. Read the answer for the missing quantity; the working panel shows the exact rearrangement used.

How it works

This tool applies Newton's second law of motion, F = m × a, where F is the net force in newtons (N), m is mass in kilograms (kg) and a is acceleration in metres per second squared (m/s²). One newton is the force that accelerates a 1 kg mass at 1 m/s².

Depending on which field you leave blank, the calculator rearranges the same equation: force is F = m × a, acceleration is a = F ÷ m, and mass is m = F ÷ a. It uses the net (resultant) force — the single force equivalent to all forces acting on the object combined.

Worked example

Force to accelerate a 10 kg mass at 9.81 m/s². A 10 kg object is accelerated at 9.81 m/s² (roughly free-fall on Earth). Enter Mass = 10 kg and Acceleration = 9.81 m/s², leaving Force blank. The calculator applies F = m × a = 10 × 9.81 = 98.1 N. That is also the object's weight, since gravity produces an acceleration of about 9.81 m/s².

Common mistakes

  • Using weight in kilograms-force or pounds instead of force in newtons. Convert to newtons first (e.g. multiply a mass in kg by 9.81 to get its weight in N).
  • Entering grams as kilograms or cm/s² as m/s². Mixed units give the wrong answer — keep everything in kg, N and m/s².
  • Using a single applied force when other forces (friction, gravity, drag) also act. F in F = m × a is the net force, not just the push you apply.

Frequently asked questions

What is the formula for force, mass and acceleration?

Newton's second law: F = m × a, where F is net force in newtons, m is mass in kilograms and a is acceleration in metres per second squared. Rearranged, a = F ÷ m and m = F ÷ a.

How do I calculate acceleration from force and mass?

Divide the net force by the mass: a = F ÷ m. For example, a 500 N net force on a 50 kg object gives 500 ÷ 50 = 10 m/s².

Is the force in F = ma the same as weight?

Only when the acceleration is gravity. An object's weight is its mass times gravitational acceleration (about 9.81 m/s² on Earth), so a 10 kg mass weighs about 98.1 N. In general F = m × a uses whatever net acceleration the object actually has.

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