Compute force, mass, or acceleration — F = m · a
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Every time you push a shopping cart, throw a ball, or step on the gas pedal, you’re experiencing Newton’s second law in action. This fundamental principle of physics force equals mass times acceleration is the key to understanding how objects move and interact. But calculating any of these three variables from the other two shouldn’t require a physics degree.
This Newton’s second law calculator lets you compute force, mass, or acceleration with just a few clicks. Choose the variable you need, enter the other two, and the tool handles the rest including automatic unit conversions and multiple display formats. Whether you’re a student checking homework, an engineer performing quick calculations, or a curious mind exploring the physics of motion, this calculator delivers accurate results instantly. All computations run locally in your browser, keeping your work private.
How to Use the Newton’s Second Law Calculator
Choose what you want to solve for Force (F), Mass (m), or Acceleration (a) — using the mode buttons at the top.
Enter the two known values in their respective input fields.
Select the appropriate units for each input from the dropdown menus.
Review the calculated result, along with mass and acceleration displayed in multiple unit systems.
Use the Copy button to save a complete summary or Share to send results to others.
The calculator applies Newton’s second law of motion, which states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Depending on which variable you’re solving for, the tool uses one of three formula variations.
Formula: F = m · a (Force = mass × acceleration)
Derived Formula: m = F / a (Mass = force ÷ acceleration)
Derived Formula: a = F / m (Acceleration = force ÷ mass)
All inputs are converted to SI base units before computation: mass to kilograms, acceleration to meters per second squared, and force to newtons. Results are displayed in multiple unit systems for convenience, force in newtons, kilonewtons, and pound-force; mass in kilograms, grams, and pounds; acceleration in m/s², ft/s², and g-forces.
A 5 kg object accelerates at 3 m/s². What force is acting on it?
Step 1: Identify the known values
m = 5 kg
a = 3 m/s²
Step 2: Apply the formula
F = m × a = 5 × 3 = 15 N
Interpretation: The object experiences a force of 15 newtons. This is the net force — the vector sum of all forces acting on the object.
If we wanted to find the mass instead: Suppose a 15 N force produces an acceleration of 3 m/s². What is the mass?
m = F/a = 15/3 = 5 kg
If we wanted to find the acceleration: A 5 kg object experiences a 15 N force. What’s the acceleration?
a = F/m = 15/5 = 3 m/s²
Newton’s second law states that the force on an object equals its mass times its acceleration. In simpler terms: heavier objects need more force to accelerate, and larger forces produce more acceleration for the same mass.
The formula is F = ma, where F is force in newtons, m is mass in kilograms, and a is acceleration in meters per second squared.
Multiply the mass by the acceleration: F = m × a. For example, 10 kg × 2 m/s² = 20 N.
Divide force by acceleration: m = F/a. For example, 20 N ÷ 2 m/s² = 10 kg.
Divide force by mass: a = F/m. For example, 20 N ÷ 10 kg = 2 m/s².
Mass is the amount of matter in an object, measured in kilograms. Weight is the force of gravity on that mass, measured in newtons. Weight = mass × gravity (W = mg). Your mass is the same everywhere, but your weight changes with gravity.
The calculator supports mass in kg, g, lbs, and oz; acceleration in m/s², ft/s², and g-forces; and force in N, kN, and lbf. All conversions are handled automatically.
Yes, for objects with constant mass and when acceleration is measured relative to an inertial frame. In more complex situations (variable mass, relativistic speeds), the formula is generalized, but F = ma is the fundamental form for most everyday physics.
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