KE to Velocity Calculator

Turn energy and mass into velocity in seconds. Switch between models and unit systems easily. Download CSV or PDF, then compare multiple scenarios quickly.

Calculator

Pick what you want to solve for.
Use relativistic near significant fractions of c.
0–12 decimals supported.
Scientific helps with extreme values.
Supports J, kJ, eV, calories, and more.
Includes kg, grams, pounds, and slugs.
Relativistic model requires v < c.
Used when solving for velocity.
Displays conversions and equations used.
Reset Tip: Use commas in large numbers.

Example Data Table

KE Mass Model Velocity (approx.) Notes
2500 J 2.5 kg Classical 44.721 m/s Everyday mechanics scale
10 kJ 0.2 kg Classical 316.228 m/s Fast but still non-relativistic
1 MJ 50 kg Classical 200.000 m/s Large energy, heavy mass
1 GeV 1.0e-27 kg Relativistic Near c Particle-scale example
500 Wh 10 kg Classical 600.000 m/s Energy-like battery units

Values are rounded and depend on selected precision and units.

Formula Used

Classical (low-speed)
  • KE = ½ m v2
  • v = √(2KE / m)
  • m = 2KE / v2
Relativistic (high-speed)
  • KE = (γ − 1) m c2
  • γ = 1 / √(1 − v2/c2)
  • v = c √(1 − 1/γ2)
c = 299,792,458 m/s

How to Use This Calculator

  1. Select a calculation mode, then choose a physics model.
  2. Enter the required two values and select their units.
  3. Pick output speed units, precision, and notation if needed.
  4. Press Calculate to view the result above.
  5. Use the export buttons to download CSV or PDF.

If the computed speed is a noticeable fraction of c, prefer the relativistic model for better accuracy.

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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.