ONE FORMULA, ONE ANSWER
Nuclear Reaction Q Value Calculator
Calculate the energy release or absorption per reaction from the total rest-mass difference. Choose input units and calculate one value within the stated conditions.
Inputs
Calculations run in this browser. Scientific notation such as 1.2e-3 is supported. Do not group thousands.
Result
Q value per reaction
Enter values and select Calculate.
Q = [Σ(Nᵢmᵢ)_initial − Σ(Nⱼmⱼ)_final]c²
Assumptions
Each mass is the rest mass of one particle or atom, multiplied by a positive integer count. Zero-rest-mass photon entries are allowed. Positive Q means energy release and negative Q means absorption. Use one consistent nuclear or atomic mass convention. Atomic masses require balanced bound-electron counts and separate checks of electronic binding and excitation corrections. The app does not validate charge or nucleon conservation, reaction feasibility or kinetic thresholds. The default 2u+3u→4.98u example is synthetic and represents no actual isotope. Input mass precision limits the accuracy of small mass differences.
Displayed values are floating-point approximations. Design safety factors and unprovided error contributions are not calculated.
Formula references and credits
- OpenStax · Nuclear fusion and Q value
- NIST · 2022 CODATA fundamental constants
- NIST · 2022 CODATA complete constants table
NaNa Lab created the code, descriptions, icons and preview images. Text, figures and code from the linked references have not been reproduced.
Physical constants: NIST / CODATA 2022. The values of μ₀ and ε₀ are measured recommendations, not exact defining constants. Values and precision notes are in the source record.
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