Kinetic Energy Calculator
Find translational kinetic energy, mass or speed from the other two values. Choose explicit units, compare energy equivalents and see how energy changes with speed.
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Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Convert mass to kilograms and speed to meters per second, then calculate half the mass times speed squared. Rearrange the equation to solve mass or non-negative speed. Convert the energy from joules to the requested unit.
Eₖ=½mv²; v=√(2Eₖ/m); m=2Eₖ/v²
Worked example
A mass of 1000 kg moving at 36 km/h (10 m/s) has kinetic energy 0.5×1000×10² = 50,000 J = 50 kJ. Doubling the speed to 72 km/h makes the energy 200 kJ.
Assumptions and input details
This is classical translational kinetic energy, valid at speeds much lower than the speed of light. It omits rotational energy, deformation, losses and relativistic corrections. Mass must be positive; known energy and speed must be non-negative. Solving mass requires both positive energy and positive speed, because zero speed cannot determine mass. Thermochemical calorie and kilocalorie are explicitly defined as 4.184 J and 4184 J.
References: OpenStax: kinetic energy · NIST: energy conversion factors
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
The 19 mass definitions distinguish avoirdupois and troy measures, metric and regional measures. Japanese kin is 600 g; mainland Chinese shijin is 500 g.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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