Mechanics & Energy Calculators
Five calculators covering the core of classical mechanics — force, moment, work, power and energy, all in consistent SI units.
One chain of ideas, five tools
These are not five unrelated formulas — they are one chain. A Force Calculator applies F = m·a. Apply that force at a distance from a pivot and you get a moment, from the Torque Calculator. Move the force through a distance and you have done work, from the Work Calculator. Divide that work by the time it took and you have power, from the Power Calculator. Give the mass a velocity and the energy is kinetic, from the Kinetic Energy.
Units are where the marks are lost
Every tool here works in SI base units: newtons, metres, seconds, kilograms, joules and watts. Mixing grams with metres, or millimetres with newtons, produces an answer that is out by a factor of a thousand and looks entirely plausible. Convert first with the Weight Converter or the Length Converter, then calculate.
Torque and work share a formula but not a meaning
Both are force multiplied by distance, and both come out as newton-metres dimensionally — but torque is a rotational effect measured in N·m and work is energy measured in joules. They are not interchangeable. The distinction is direction: in work the force acts along the displacement; in torque it acts perpendicular to the lever arm.
Going further
For material behaviour under those loads, move to the Stress Calculator and the rest of the materials tools. Every formula on this page is listed with its symbols on the engineering formulas reference reference page.
Idealised conditions, and what they leave out
Every calculator here assumes a rigid body, a point of application, and no losses. Real mechanisms lose energy to friction, deflect under load, and rarely apply force perfectly along or perpendicular to the axis you assumed. The practical consequence is that measured power at a shaft is always lower than calculated input power, and the gap is efficiency. Two habits close most of the distance between a textbook answer and a working one: resolve forces into components before applying any formula rather than assuming alignment, and sanity-check the magnitude — a person can sustain roughly 100 W of mechanical output, a family car peaks near 100 kW, so an answer three orders of magnitude off usually means a unit error rather than a physics error.
Frequently asked questions
What units should I enter?＋
SI base units throughout: kilograms, metres, seconds, newtons, joules and watts. The single most common error on these tools is entering grams or millimetres, which puts the answer out by a factor of a thousand or a million while still looking plausible. Convert first, then calculate.
Torque and work are both force times distance — are they the same thing?＋
No. Dimensionally they look identical, but in work the force acts along the displacement and the result is energy in joules; in torque the force acts perpendicular to a lever arm and the result is a rotational effect in newton-metres. The two are never interchangeable, and quoting torque in joules is a marking error.
Why does my measured power not match the calculated figure?＋
Because these formulas assume no losses. Friction, windage, deflection and imperfect force alignment all take a share, so real output at a shaft is always below calculated input. The ratio between them is efficiency, and for common machinery it typically sits somewhere between 70% and 95%.
Can I use these for coursework?＋
Yes, as a check. They show the formula and the substitution, which is what markers award method marks for. What they cannot do is resolve a diagram for you — deciding which forces act where is the part that carries the marks, and the part the calculator assumes you have already done.