Energy units converter
Energy units converter. Converts joules, calories, many physical, british, american and time related units.

Inputs data - value and unit, which we're going to convert

1 (joule) is equal to:

common use


metric (SI)



British thermal unit (thermochemical)BTUth0.000948452
British thermal unit (ISO)BTUISO0.000948317
British thermal unit (63 °F)BTU63 °F0.000948227
British thermal unit (60 °F)BTU60 °F0.000948155
British thermal unit (59 °F)BTU59 °F0.000948043
British thermal unit (International Table)BTUIT0.000947817
British thermal unit (mean)BTUmean0.000947086
British thermal unit (39 °F)BTU390.00094369
cubic foot of atmospherecu ft atm; scf0.000348529
cubic yard of atmospherecu yd atm; scy0.000012908
cubic foot of natural gas9.478171203×10-7
foot-poundalft pdl23.730360404
foot-pound forceft lbf0.737562149
gallon-atmosphere (US)US gal atm0.002607175
gallon-atmosphere (imperial)imp gal atm0.002170928
inch-pound forcein lbf8.850745791
therm (U.S.)9.48043428×10-9
therm (E.C.)9.478171203×10-9

calories related

calorie (20 °C)cal20 °C0.239125756
calorie (thermochemical)calth0.239005736
calorie (15 °C)cal15 °C0.238920081
calorie (International Table)calIT0.238845897
calorie (mean)calmean0.238662345
calorie (3.98 °C)cal3.98 °C0.237840409
large calorieCal0.000238846


atomic unit of energyau2.293712658×1017
Celsius heat unit (International Table)CHUIT0.000526565
cubic centimetre of atmosphere; standard cubic centimetrecc atm; scc9.869232667
erg (cgs unit)erg10000000
litre-atmospherel atm0.009869233

time related


materials related

barrel of oil equivalentbboe1.633986928×10-10
ton of TNTtTNT2.390057361×10-10
ton of coal equivalentTCE3.412084238×10-11
ton of oil equivalentTOE2.388458966×10-11

Some facts

  • Energy is the scalar physical quantity expressing the ability to do the work.
  • Energy is additive. This means that the total energy of the system consisting of the N objects, is the sum of the energy of each of the bodies.
  • The kinetic energy is work to be done in order to provide the body with mass m, velocity V. It amounts to Ekinetic = mV2/2, where Ekinetic is the kinetic energy, m is the mass, and V is the value of the velocity vector.
  • The potential energy at the point x0 is work to be done to put the body at this point (moving them from infinity).
    • There are many different symbols used for potential energy depending on kind of science. Most common are U, V, or simply Epot..
    • Potential energy can be negative. This means that we don't need to perform the work to put the body in the current positions at all, but also it is needed to do the work to corrupt current system. In this case we say that system is in a bound. A good example here are chemical molecules that are associated systems, because we need to do work to break chemical bonds.
    • The function U=f(x), which assigns value of potential energy to each point x is commonly called potential energy surface. Sometimes, when people want to mark that surface have more than 3 dimensions (degree of freedom), they use term hipersurface. The concept of (hiper)surface of potential energy is widely used for example in quantum chemistry or physics of the atomic nucleus.
  • There are many forms of energy for example: heat or electrical.
  • The basic energy unit in SI system is 1J (one jul), so it's the same as unit of work. However, for practical reasons many different units are used depending on kind of science for example:
    • elektronovolts (eV) in high-energy physics,
    • atomic units (au) in quantum chemistry,
    • calories in dietetic,
    • horsepower in automotive industry.
  • The average kinetic energy of single particle divided by the number of degrees of freedom is temperature of the system. Such concepts owe the development of statistical thermodynamics (physics), which made it possible to link the micro state (individual particles level) with macroscopic quantities (such as temperature, pressure). Previously, the concept of micro and macroscopic were independent. It is worth noting that the concept of temperature has only statistical meaning. This means for example that temperature for single particle has no meaning.
  • One of the fundamental laws of nature is the desire to minimize energy. There are no known causes of this fact, but an enormous amount of physical theory is based on this postulate. Very often the solution to a practical problem boils down to mininimalization energy problem. Examples include:
    • Molecular mechanics - the way of finding optimal molecule geometry using clasical Newton dynamic.
    • Variational methods - the set of general methods, that searches for wave functions, for which the system gives minimal average energy (formally the average value of the Hamiltonian). Good examples are Hartree-fock equations, which (together with Density Functional Theory - DFT) are the foundations of modern quantum-mechanical calculations.
    • Chemical reaction paths - sets of methods trying to search for optimal trace on energy surface.
    A common feature of all of the above examples, it is asking "what to do to reach a minimum of energy."
    From a mathematical point of view, that are classic optimization problems. Mathematical apparatus that deals with this kind of problem is - depending on whether we are looking for the numbers or functions - calculus or calculus of variations.
  • If we have the potential energy surface, we can get forces that operate in various points in the system. To do this we need to calculate the energy derivative dE/dx in point. This fact is due to the reversal of the definition of work (integral of the product of the displacement and the applied force). Such a procedure may be used for numerical optimization of the geometry of the system. To do this we need to repeat in loop (as long as there are forces in the system):
    • Compute forces working for each particle (by computing derivate dE/dx).
    • Move particles by computed forces.
    Above procedure is widely used in many numerical simulations for example in quantum chemistry.

How to convert

  • Enter the number to field "value" - enter the NUMBER only, no other words, symbols or unit names. You can use dot (.) or comma (,) to enter fractions.
    • 1000000
    • 123,23
    • 999.99999
  • Find and select your starting unit in field "unit". Some unit calculators have huge number of different units to select from - it's just how complicated our world is...
  • And... you got the result in the table below. You'll find several results for many different units - we show you all results we know at once. Just find the one you're looking for.

Tags and links to this website


This is permalink. Permalink is the link containing your input data. Just copy it and share your work with friends:

Links to external sites (leaving Calculla?)

Ancient version of this site - links

"Calculla v1" version of this calculatorIn December 2016 the Calculla website has been republished using new technologies and all calculators have been rewritten. Old version of the Calculla is still available through this link: We left the version 1 of Calculla untouched for archival purposes.
Direct link to the old version:
JavaScript failed !
So this is static version of this website.
This website works a lot better in JavaScript enabled browser.
Please enable JavaScript.