Physics Calculator
Choose what you want to find, enter the values you know, and get the answer with its SI unit and the relation used. The calculator covers seven basic mechanics laws and solves each one for any of its unknowns. All units are SI: meters, kilograms, seconds, newtons and joules.
Last updated November 3, 2026
Magnitude above 0, up to 1,000,000,000,000,000 m.
Magnitude above 0, up to 1,000,000,000,000,000 s.
Result
Speed = 5 m/s
| Measure | Value |
|---|---|
| Speed | 5 m/s |
| Relation used | v = d ÷ t |
| Distance | 100 m |
| Time | 20 s |
SI units only (meters, kilograms, seconds). All values are magnitudes above 0. Results show up to 6 significant digits.
Show the work
Formula: v = d ÷ t, rearranged for speed: v = d ÷ t
- You entered distance 100 m, time 20 s.
- Rearrange: v = d ÷ t.
- Substitute: v = 100 ÷ 20.
- Calculate: v = 5 m/s.
Result: Speed = 5 m/s
The seven relations behind the calculator
v = d ÷ t
F = m × a
p = m × v
KE = ½ × m × v²
PE = m × g × h
W = F × d
P = W ÷ t
Speed is distance divided by time, so 100 m covered in 20 s is 5 m/s. Force is mass times acceleration, so a 10 kg object accelerating at 2 m/s² needs 20 N. Momentum is mass times speed, so 10 kg moving at 5 m/s carries 50 kg·m/s.
Kinetic energy is half the mass times the speed squared, so the same 10 kg at 5 m/s has ½ × 10 × 5² = 125 J. Gravitational potential energy is mass times g times height. With g set to the standard value of 9.80665 m/s², lifting 10 kg by 10 m stores 980.665 J.
Work is force times distance, so 20 N over 5 m is 100 J. Power is work divided by time, so 200 J delivered in 4 s is 50 W. Each relation can be rearranged for any unknown.
See how we calculate for the formulas, sources and review schedule behind every calculator.
Also useful alongside this calculator: Length Converter.
Converting to SI units before you enter numbers
The fields expect meters, kilograms and seconds. To turn kilometers per hour into meters per second, divide by 3.6: 90 km/h is 25 m/s. For miles per hour, multiply by 0.44704, so 60 mph is 26.8224 m/s.
Pounds convert to kilograms with 0.45359237, so 150 lb is about 68.04 kg. Minutes and hours become seconds by multiplying by 60 and 3600, and kilometers become meters by multiplying by 1000.
Solving for mass, time or speed instead
Any relation can be turned around. A force of 5 N on a 2 kg object gives an acceleration of 5 ÷ 2 = 2.5 m/s². A trip of 100 km in 2 h is 100,000 m in 7,200 s, which is a speed of about 13.89 m/s.
Kinetic energy needs a square root when you solve for speed: v = √(2 × E ÷ m). Potential energy works the other way, so 1,000 J lifts a 5 kg object to about 20.39 m under standard gravity.
Each field accepts magnitudes only, meaning numbers above 0 and up to one quadrillion. Zero, negative numbers and blanks are rejected with a message, because a zero would divide by zero or make the result meaningless.
What this calculator does not cover
It applies one formula at a time. It does not solve constant-acceleration kinematics such as s = ut + ½at², and it does not chain several steps, so for a falling object you would work out each quantity separately.
It ignores friction, air resistance, rotation and direction. Force and momentum are vectors in real problems, but here only their size is used. At speeds close to the speed of light, relativity changes these formulas and they no longer apply.
How to use the Physics Calculator
- Open the menu and choose what you want to find, such as Force from mass and acceleration.
- Convert your values to meters, kilograms and seconds if they are in other units.
- Fill in the fields that appear, using numbers above 0.
- Read the answer, its unit and the relation used, then open Show the work to check each substitution.
Worked example
A 1,200 kg car travels at 25 m/s, which is 90 km/h. Its momentum is 1,200 × 25 = 30,000 kg·m/s and its kinetic energy is ½ × 1,200 × 25² = 375,000 J. Doubling the speed to 50 m/s makes the kinetic energy four times larger, 1,500,000 J. Pushing the car at 2.5 m/s² needs 3,000 N, which does 120,000 J of work over 40 m and, if done in 8 s, a power of 15,000 W.
| Quantity | Inputs | Result |
|---|---|---|
| Momentum | 1,200 kg at 25 m/s | 30,000 kg·m/s |
| Kinetic energy | 1,200 kg at 25 m/s | 375,000 J |
| Force | 1,200 kg at 2.5 m/s² | 3,000 N |
| Work | 3,000 N over 40 m | 120,000 J |
| Power | 120,000 J in 8 s | 15,000 W |
Frequently asked questions
Which units does the physics calculator use?
It uses SI units only: meters, kilograms and seconds, with newtons, joules, watts and kg·m/s for the results. Convert miles, pounds or hours before you enter them.
What value of gravity is used for potential energy?
The default is 9.80665 m/s², the conventional standard gravity. You can type another value, for example 1.62 m/s², and 10 kg raised 10 m then stores 162 J.
Why does doubling the speed quadruple the kinetic energy?
Kinetic energy depends on the square of the speed. Going from 25 m/s to 50 m/s multiplies the speed by 2 and the energy by 4, so a 1,200 kg car goes from 375,000 J to 1,500,000 J.
Can I enter negative numbers or zero?
No. Every input must be a number above 0 and at most 1,000,000,000,000,000, because the page works with magnitudes. Direction is not modelled, and zero would cause a division by zero in some rearrangements.
Does it handle friction, air resistance or acceleration over time?
No. It solves single formulas for ideal cases and leaves out friction, drag, rotation and relativity. For motion with changing speed over time, you need a constant-acceleration kinematics tool.