Force Calculator – F = ma in Newtons and Pounds
This force calculator uses Newton's second law, force equals mass times acceleration, to solve for any one of the three values. Choose force, mass or acceleration as the unknown, enter the other two with the units you like, and get the answer in newtons, pounds-force and kilogram-force. It accepts kilograms or pounds for mass and meters per second squared, feet per second squared or g for acceleration. It also shows the weight of the mass on Earth for comparison. Use it for physics homework, engineering estimates and quick checks, all calculated in your browser.
Force Calculator
Solve force, mass or acceleration with Newton's second law.
How to use the Force Calculator
- Choose what to solve for: force, mass or acceleration.
- Enter the two known values.
- Pick the unit for each value.
- Read the answer in several units.
- Copy the result for your notes.
Newton's second law
F = m × a. In SI units, force is in newtons, mass in kilograms and acceleration in meters per second squared. The calculator converts your units to SI, solves for the unknown and converts the answer back.
Features
- Solves F = ma for any variable
- Newtons, pounds-force and kilogram-force
- Mass in kg or lb
- Acceleration in m/s², ft/s² or g
- Shows weight on Earth
- Copy and print
Frequently asked questions
What is the formula for force?
Force equals mass times acceleration, F = m × a. With mass in kilograms and acceleration in meters per second squared, the force is in newtons.
What is a newton?
One newton is the force needed to accelerate a 1 kg mass at 1 m/s². It is about the weight of a small apple.
How do I convert newtons to pounds-force?
Divide newtons by 4.44822 to get pounds-force. One pound-force is about 4.448 N.
How do I find the force of a 10 kg object accelerating at 3 m/s²?
Multiply 10 by 3 to get 30 N, which is about 6.74 lbf.
Is weight the same as mass?
No. Mass is how much matter an object has and weight is the force of gravity on it. Weight in newtons is mass in kilograms times 9.80665.