Force calculator (Newton's second law)
Calculate net force with Newton's second law: force = mass × acceleration.
How the calculation works
Newton's second law states that net force equals mass times acceleration:
F = m × a
With mass in kg and acceleration in m/s², force comes out in newtons (N). Weight is a special case, with a = g ≈ 9.8 m/s².
Examples
- 10 kg accelerating at 2 m/s²: F = 10 × 2 = 20 N.
- The weight of 70 kg on Earth: 70 × 9.8 = 686 N.
Frequently asked questions
What is 1 newton?
It's the force that gives 1 kg an acceleration of 1 m/s². 1 N ≈ 0.102 kgf.
Mass vs weight?
Mass (kg) is the amount of matter; weight is gravity's force on it (F = m × g), in newtons.
What is net force?
It is the vector sum of all forces on the object. Only it accelerates the body — if zero, velocity stays constant.
Related calculators
Kinetic energy
Calculate the kinetic energy of a body from its mass and speed.
Potential energy
Calculate gravitational potential energy (E = m·g·h) and the speed the body would reach if it fell.
Acceleration
Calculate acceleration from the initial and final velocity and the time — plus the distance traveled.
More Physics calculators
See all →Average speed
Calculate average speed from distance and time, in km/h and m/s.
Ohm's law
Calculate voltage, current or resistance with Ohm's law, plus the circuit power.
Density
Calculate density from mass and volume (d = m ÷ V), in g/cm³ and kg/m³.
Free fall
Work out how long an object takes to fall and how fast it lands. Example: from 20 meters it takes ~2 seconds and ends at roughly 71 km/h.
Equivalent resistance
Combine resistors in series or parallel to get the circuit's equivalent resistance.
Work and power
Calculate the work of a force (W = F·d) and the power (P = W/t), in joules, watts and hp.
Speed, distance and time
Calculate the speed, distance or time of a trip from the other two values.
Updated on June 30, 2026 · by Rafael Rossi · Methodology & sources