Force
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Force, Mass & Acceleration (F=ma) Newton Calculator
Fill any two of force, mass, and acceleration (0 means unknown) using F = m a.
Page updated 2026-09-04.
Calculator
Calculated Results
Mass
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Acceleration
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Newton's second law, solved for the missing variable
With mass 10 and acceleration 2 (and force left at 0 to mark it unknown), the calculator solves F = 20 -- Newton's second law, F = m x a, applied to find force from the other two known values.
Like the speed/distance/time calculator, this same formula rearranges depending on which variable is left at zero: force = mass x acceleration, mass = force / acceleration, or acceleration = force / mass -- the underlying relationship between the three variables never changes, only which one you're solving for.
10 x 2 = 20 in standard SI units means 20 newtons of force -- a newton is itself defined as the force needed to accelerate 1 kilogram at 1 meter per second squared, which is exactly why this formula and these specific units fit together so cleanly.
Why SI units specifically make this formula work cleanly
SI-style units: newtons, kilograms, m/s^2. 0 marks the unknown. Using kilograms for mass, meters per second squared for acceleration, and newtons for force keeps the formula in its simplest form with no extra conversion factor needed -- mixing in non-SI units (like pounds for mass or a different acceleration unit) would require an additional conversion constant that this calculator doesn't apply automatically.
This is Newton's second law in its most basic form, which assumes a single, constant net force acting on a single object with unchanging mass -- more complex scenarios (multiple forces acting at different angles, changing mass like a rocket burning fuel) would need a more elaborate analysis beyond this simple three-variable relationship.
As with the speed/distance/time tool, exactly two of the three fields need real, nonzero values for the calculator to solve for the third -- leaving more than one field at zero means there isn't enough information to find a unique answer.
Related physics tools
For calculating the kinetic energy that results from an object's mass and velocity (a related but distinct physics quantity from force), the Kinetic & Potential Energy Calculator is the next related calculation.
For the equivalent solve-for-the-unknown structure applied to motion instead of force, the Speed, Distance & Time Calculator uses the same approach.
Frequently Asked Questions (FAQ)
How is F = 20 calculated from mass 10 and acceleration 2?
Using Newton's second law: Force = mass x acceleration = 10 x 2 = 20 newtons, given standard SI units for mass (kg) and acceleration (m/s²).
Why does using SI units (kg, m/s², newtons) matter for this formula?
SI-style units: newtons, kilograms, m/s^2. 0 marks the unknown. A newton is defined specifically as the force needed to accelerate 1 kg at 1 m/s², so F = m x a works cleanly with no extra conversion factor only when mass and acceleration are already in those specific SI units. Other unit systems would need an additional constant applied.
How do I solve for mass or acceleration instead of force?
Enter the other two known values and leave the field you want solved for at 0 -- mass = force / acceleration, or acceleration = force / mass, following the same rearranged relationship.
Does this account for multiple forces acting on an object at once?
No. This models a single net force on an object with constant mass. Multiple forces acting at different angles, or a changing mass (like a rocket burning fuel), would require a more elaborate analysis beyond this simple three-variable relationship.
What happens if I leave more than one field at zero?
SI-style units: newtons, kilograms, m/s^2. 0 marks the unknown. The calculator needs exactly two known nonzero values to solve for the third -- with only one known value, there isn't enough information to uniquely determine the other two.
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