Energy Density Calculator
Stored energy per volume.
The number that decides technologies
u = U / V
Gasoline stores about 34 GJ/m³, lithium-ion batteries around 2.5 GJ/m³, and a supercapacitor a tenth of that: a thirteen-fold gap that shapes everything about cars, planes and phones. The same formula covers fields: a capacitor's dielectric and a magnet's gap store energy at ½εE² and B²/2μ joules per cubic meter.