E=mc² Calculator
Calculate e=mc² instantly in your browser — the published formula, worked locally with no data sent anywhere.
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What this tool does
Calculate e=mc² instantly in your browser — the published formula, worked locally with no data sent anywhere. This is the total rest energy locked in the mass — real processes (fission, fusion, annihilation) convert only a small fraction of it. 1 kiloton of TNT = 4.184×10¹² J by definition.
How to use the E=mc² Calculator
- Enter or select mass (kg).
- Read the calculated result; change any measurement to compare alternatives.
Formula
mass–energy equivalence: E = m × c², with c = 299,792,458 m/s, so 1 kg of mass corresponds to 8.9876×10¹⁶ joules.
- mass
- Mass (kg)
This is the total rest energy locked in the mass — real processes (fission, fusion, annihilation) convert only a small fraction of it. 1 kiloton of TNT = 4.184×10¹² J by definition.
Worked example
For e=mc² calculator, the following measurements illustrate the exact method: Mass (kg): 1.
Inputs
- Mass (kg)1
Result
- Energy (J)89,875,517,873,681,760
- Energy (kWh)24,965,421,631.58
- Equivalent (kilotons of TNT)21,480.76
- Equivalent (megatons of TNT)21.48
Results explained
- Energy (J)
- Energy (J) from the formula above. This is the total rest energy locked in the mass — real processes (fission, fusion, annihilation) convert only a small fraction of it. 1 kiloton of TNT = 4.184×10¹² J by definition.
- Energy (kWh)
- Energy (kWh) from the formula above. This is the total rest energy locked in the mass — real processes (fission, fusion, annihilation) convert only a small fraction of it. 1 kiloton of TNT = 4.184×10¹² J by definition.
- Equivalent (kilotons of TNT)
- Equivalent (kilotons of TNT) from the formula above. This is the total rest energy locked in the mass — real processes (fission, fusion, annihilation) convert only a small fraction of it. 1 kiloton of TNT = 4.184×10¹² J by definition.
- Equivalent (megatons of TNT)
- Equivalent (megatons of TNT) from the formula above. This is the total rest energy locked in the mass — real processes (fission, fusion, annihilation) convert only a small fraction of it. 1 kiloton of TNT = 4.184×10¹² J by definition.
Frequently asked questions
mass–energy equivalence: E = m × c², with c = 299,792,458 m/s, so 1 kg of mass corresponds to 8.9876×10¹⁶ joules.
This is the total rest energy locked in the mass — real processes (fission, fusion, annihilation) convert only a small fraction of it. 1 kiloton of TNT = 4.184×10¹² J by definition.
Every field is labelled with its unit — enter values in exactly the labelled unit and read the result in the labelled output unit. Fields with a unit symbol also support the site-wide imperial/metric switch, which converts before the formula runs.
It uses double-precision arithmetic and the published constants and formulas named on this page. The last displayed digit may be rounded, and real conditions can differ from the idealized model described in the assumptions.
Yes. Every calculation runs entirely in your browser; nothing you enter is uploaded, stored or shared.