Mass–Energy Conversion Calculator

Accurate rest‑energy estimates with unit controls, constants, and clear outputs quickly anywhere. Compare joules, eV, and TNT, then download your calculation summary as files.

Calculator

Switching mode updates unit choices.
Shown as the headline result above.
Default is vacuum value; override for sensitivity checks.
Result appears above the form after calculation.

Formula Used

The calculator applies Einstein’s mass–energy equivalence for rest energy: E = m c². For the inverse conversion, it rearranges to m = E / c².

  • E is energy in joules (J).
  • m is mass in kilograms (kg).
  • c is the speed of light in m/s (default 299,792,458).

How to Use

  1. Select Mass → Energy or Energy → Mass.
  2. Enter a non‑negative value and choose its unit.
  3. Pick a primary energy unit for the headline result.
  4. Adjust c and significant figures if needed.
  5. Click Calculate, then download CSV or PDF if required.

Example Data Table

Mass (kg) Energy (J) Energy (Mt TNT) Energy (GeV)
1.0e-68.98755e+102.14808e-55.60959e+20
0.0018.98755e+130.02148085.60959e+23
18.98755e+1621.48085.60959e+26
108.98755e+17214.8085.60959e+27
Values assume vacuum c and rest energy only.

Use mass–energy conversion to link matter and power precisely.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.