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Muzzle Energy Calculator

Calculate muzzle energy in ft-lbs from bullet weight and muzzle velocity. Compare cartridge power for hunting and ballistic performance.

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Inputs that matter
Bullet Weight, Velocity, Powder Charge (optional)
Output to expect
Muzzle Energy Calculator
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Kinetic Energy Formula

Energy equals one-half mass times velocity squared. Use bullet weight in grains and velocity in fps for ft-lbs result.

Energy (ft-lbs) = (weight gr × velocity² fps) / 450,400

Energy at Distance

Energy decreases as velocity drops from air drag. Retained energy at range requires velocity at that distance from trajectory solver.

E_downrange = (weight × V²) / 450,400

Joules Conversion

Metric energy in joules: multiply grains to grams, fps to m/s, apply ½mv².

Joules = (weight gr × 0.0648 × velocity fps × 0.3048²) / 2

Updated: July 2026

Example Scenarios

Energy = (100 × 2960²) / 450,400 ≈ 1,945 ft-lbs. Adequate for deer at moderate ranges with proper bullet construction.

Energy = (124 × 1150²) / 450,400 ≈ 364 ft-lbs. Typical self-defense load — energy alone does not determine terminal performance.

Energy ≈ 4,260 ft-lbs. Large bore African game cartridge — retained energy at 200 yards still exceeds 3000 ft-lbs.

Common Mistakes to Avoid

Judging hunting adequacy by muzzle energy alone

Energy at the animal matters, not at the muzzle. Calculate retained energy at max hunting range using trajectory data, and select bullets designed for game size.

Using grain weight without confirming actual bullet weight

Cast bullets and some handloads vary ±2–3 grains from nominal. For energy calculations within 5%, nominal weight is fine; for precision, weigh bullets.

FAQ

Traditional guideline: 1000 ft-lbs minimum at impact. Modern bonded and monolithic bullets perform well with less if placement is good — but 1000 ft-lbs at target remains a useful benchmark.

No. Terminal performance depends on bullet construction, expansion, shot placement, and tissue disruption — not energy alone. A sharp arrow kills without high ft-lbs.

Kinetic energy = ½mv². Doubling velocity quadruples energy; doubling weight only doubles energy. Velocity is the dominant lever for energy increase.

Compare energy at expected impact distance, not just muzzle. A fast light bullet may have high muzzle energy but less retained energy at 300 yards than a heavier slower bullet.

In ballistics, ft-lbs and ft-lbf (foot-pounds force) are used interchangeably for energy. Strictly, energy is ft-lbf in technical units — context makes meaning clear.

About Muzzle Energy Calculator

Muzzle energy quantifies a bullet's kinetic energy at the muzzle — a key metric for hunting adequacy and cartridge comparison. This calculator computes ft-lbs and joules from bullet weight and chronographed velocity.