Primary formula
E = W = F x d x cos(theta); E = P x t; Q = m x c x Delta T.
Physics calculator
Energy Calculator
Calculate energy using common physics relationships: work-energy, power multiplied by time, or heat energy from mass, specific heat and temperature change.
Last reviewed: July 21, 2026Physics mechanics engine v1.0.0
Physics calculator
Energy Calculator
Enter values, select units and calculate locally. Results use SI internally and show rounded display values.
Decimal.js physics math
Mode
Find energy from power and elapsed time.
Result and visual stay hidden until you choose Calculate.
Formula and assumptions
Input assumptions
Selected formula determines the meaning of energy. Time and mass inputs must be physically valid. Specific heat is entered in J/(kg*K).
Precision note
Physics Phase 1 converts compatible inputs into SI units before calculating. Decimal.js is used for arithmetic where practical; trigonometric angle factors are rounded for display.
Physics calculation flow
Parse
Read labelled inputs, selected units and calculation mode from the calculator card.
Convert
Convert compatible values to SI base or derived units without calling external services.
Calculate
Apply the selected deterministic mechanics formula and validate against NaN, Infinity and invalid divisors.
Label
Display the result, supporting unit rows, formula steps, warnings and dynamic visual below the input card.
What Energy Calculator does
Use this formula calculator when you need to solve an energy relationship, not only convert energy units.
The calculator is deterministic and runs from manual inputs only. It is a physics formula tool, so it should not be confused with a unit converter that only changes labels after a value is already known.
Formula and variables
E = W = F x d x cos(theta); E = P x t; Q = m x c x Delta T.
The calculator converts supported units into SI base or derived units for the actual calculation, then formats the result in the selected display unit.
- E is energy
- P is power
- t is time
- c is specific heat
- Delta T is temperature change
Worked examples
Use the examples below to check expected order of operations and unit handling before applying the tool to your own values.
- 100 W x 2 h = 720,000 J = 0.2 kWh
- 10 N x 5 m x cos(0 deg) = 50 J
- 2 kg x 4186 J/(kg*K) x 10 K = 83,720 J
Unit conversions
Length, time, mass, speed, force, energy and power units reuse the central NexaCalc conversion registry. Acceleration and spring-constant units use the same SI-first convention for mechanics formulas.
The displayed conversion rows are supporting context. They do not change the physical assumptions of the selected formula.
Common mistakes
Most errors come from mixing physical quantities that sound similar in everyday language or choosing a unit that belongs to a different dimension.
- Confusing kW and kWh.
- Using heat mode without specific heat.
- Expecting automatic efficiency or loss modelling.
Assumptions and limitations
This page is intended for educational and planning calculations, not professional engineering certification.
This calculator uses idealized physics formulas and the input values you provide. Real systems may require additional effects such as friction, drag, rotation, deformation, losses or measurement uncertainty.
- Selected formula determines the meaning of energy.
- Time and mass inputs must be physically valid.
- Specific heat is entered in J/(kg*K).
- The calculator does not include losses, phase changes, chemical reactions or thermodynamic constraints.
- Use Kinetic or Potential Energy calculators for those dedicated formulas.
Frequently asked questions
What energy formula should I choose?
Energy Calculator uses E = W = F x d x cos(theta); E = P x t; Q = m x c x Delta T. The result is calculated from the values and units entered in the form.
Is energy the same as work?
Energy Calculator is formula-based. Use the related calculator when the question changes physical quantity, and use Conversion tools only when the value is already known.
How do I calculate energy from power and time?
Energy Calculator uses E = W = F x d x cos(theta); E = P x t; Q = m x c x Delta T. The result is calculated from the values and units entered in the form.
How is heat energy calculated?
Energy Calculator uses E = W = F x d x cos(theta); E = P x t; Q = m x c x Delta T. The result is calculated from the values and units entered in the form.
Why does kWh appear in energy results?
Use this formula calculator when you need to solve an energy relationship, not only convert energy units. Selected formula determines the meaning of energy.
Does this calculator convert energy units?
Energy Calculator converts compatible inputs to SI internally, then displays the selected output unit. E is energy; P is power; t is time; c is specific heat; Delta T is temperature change.
What is the difference between kinetic and potential energy?
Energy Calculator is formula-based. Use the related calculator when the question changes physical quantity, and use Conversion tools only when the value is already known.
Why is specific heat needed for heat energy?
Use this formula calculator when you need to solve an energy relationship, not only convert energy units. Selected formula determines the meaning of energy.
Does this calculator include energy losses?
Energy Calculator uses an idealized classroom mechanics model. The calculator does not include losses, phase changes, chemical reactions or thermodynamic constraints.
When should I use the Energy Converter?
Use this formula calculator when you need to solve an energy relationship, not only convert energy units. Selected formula determines the meaning of energy.
References
- NIST Special Publication 811, Guide for the Use of the International System of Units. Relevance: SI unit symbols and derived-unit naming. Last verified: July 21, 2026. Source.
- BIPM, The International System of Units SI Brochure. Relevance: SI base and derived units used in mechanics. Last verified: July 21, 2026. Source.
- OpenStax University Physics Volume 1. Relevance: introductory mechanics formulas for motion, force, work, energy and momentum. Last verified: July 21, 2026. Source.
Physics Phase 1 references verified for SI units and mechanics formulas on July 21, 2026.
Educational disclaimer
This calculator provides mathematical results from the values, conventions and methods you enter. Verify important academic, engineering or professional work independently.