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- Uses Newton’s second law, F = ma.
- Finds force, mass or acceleration from the other two.
- Works with newtons, kN, pound-force and kgf.
- Shows the weight of the mass on Earth.
How to use the force calculator
Choose what to find
Force, mass or acceleration.
Enter the two known values
For example 10 kg and 9.81 m/s².
Pick the units
For mass, acceleration and force.
Read the result
With conversions to other units.
Newton’s second law
Newton’s second law says that the force on an object equals its mass times its acceleration. A bigger force gives more acceleration, and a heavier object needs more force for the same acceleration.
Force formulas
F = m × a
m = F ÷ a
a = F ÷ m
With mass in kg and acceleration in m/s², force is in newtons (N).
Example 1: weight of a 10 kg object
Acceleration due to gravity 9.81 m/s².
- Force 98.1 N (22.05 lbf)
Example 2: finding acceleration
100 N pushing a 10 kg object.
- Acceleration 10 m/s²
Example 3: finding mass
500 N causes 2 m/s² of acceleration.
- Mass 250 kg
Where the force formula is used
Physics class
Solve F = ma problems.
Engineering
Size motors, cables and supports.
Vehicles
Find the thrust needed to accelerate.
Weight
Work out the weight of any mass.
Find how fast something speeds up with the acceleration calculator, or its energy of motion with the kinetic energy calculator.
Force calculator FAQ
What is the formula for force?
F = m × a: force equals mass times acceleration.
What is a newton?
The force needed to accelerate 1 kg at 1 m/s².
How do I find weight?
Multiply mass by gravity. A 10 kg object weighs about 98.1 N on Earth.
What is the difference between mass and weight?
Mass is the amount of matter (kg); weight is the force of gravity on it (N).
How many newtons is one pound-force?
About 4.448 N.
Can force be negative?
Yes. A negative force acts in the opposite direction, such as braking.