Bullet Energy Calculator — Muzzle Energy & Momentum
Enter the bullet mass (grains or grams) and muzzle velocity (fps or m/s) to instantly get the muzzle energy in both joules and foot-pounds, plus momentum and the IPSC power factor.
Mass unit
Velocity unit
2,610.8 ft·lbf
Mass in kg
Velocity in m/s
Kinetic energy KE = ½mv²
- 1
Mass in kg
150 gr × 6.480×10⁻⁵ = 0.009721 grain = 6.479891 × 10⁻⁵ kg (exact). - 2
Velocity in m/s
2,800 fps × 0.3048 = 853.44 - 3
KE = ½ × m × v²
0.5 × 0.00972 × 853.44² = 3,539.8
How does this calculator work?
Muzzle energy KE = ½mv². Convert mass (grains × 6.48×10⁻⁵ = kg) and velocity (fps × 0.3048 = m/s), then KE in joules × 0.7376 = ft·lbf. Typical pistols: 200–500 J; intermediate rifle: 1 500–2 500 J; full-power rifle: 3 000–5 500 J.
Formula
How this is calculated
Bullet energy is simply the classical kinetic energy formula KE = ½mv², where m is the bullet mass in kilograms and v is the velocity in metres per second — giving energy in joules. Converting to foot-pounds of force (ft·lbf), the unit used in US ballistics, multiplies by 0.7376.
Grains (abbreviated gr) are the traditional unit of bullet mass: 1 grain = 64.8 mg exactly. Muzzle velocity in feet per second (fps) is the standard US measurement; 1 fps = 0.3048 m/s exactly. The calculator converts the raw inputs to SI before computing, then converts the result back for display.
Momentum (p = mv) in kg·m/s is a useful secondary quantity for recoil estimation — the recoil impulse on the shooter equals the forward impulse on the bullet plus propellant gases, by Newton's third law. The IPSC power factor (mass in grains × velocity in fps ÷ 1000) is a competition rule that sets minimum energy floors for different divisions (Major ≥ 160, Minor ≥ 125 as typical thresholds). These thresholds are organisation-specific and not encoded in this calculator — use the displayed power factor against your rulebook.
Frequently asked questions
Common pistol rounds: 9mm Parabellum (147 gr at 975 fps) ≈ 310 J / 230 ft·lbf; .45 ACP (230 gr at 830 fps) ≈ 360 J / 265 ft·lbf; .357 Magnum (158 gr at 1 250 fps) ≈ 740 J / 550 ft·lbf. These values vary significantly with barrel length and load.
Energy alone is not a reliable predictor of terminal effectiveness. Bullet construction, expansion, sectional density and shot placement all play major roles. Energy is a useful objective measure for comparing loads and for meeting minimum thresholds (hunting regulations, competition power factors) but does not capture the full picture of wound ballistics.
Energy (½mv²) scales with the square of velocity and is the primary factor in tissue disruption. Momentum (mv) scales linearly with velocity and is the quantity conserved during recoil — a higher-momentum load produces more felt recoil. Slower, heavier bullets carry similar energy to fast, light ones but higher momentum; they tend to be preferred for game with thick hides or heavy bones where deep penetration matters more than fragmentation.
TG we-Calculate Editorial Team. (2026). Bullet Energy Calculator — Muzzle Energy & Momentum [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/bullet-energy-calculator
TG we-Calculate Editorial Team. "Bullet Energy Calculator — Muzzle Energy & Momentum." TG we-Calculate. 2026. https://we-calculate.com/calculator/bullet-energy-calculator.
TG we-Calculate Editorial Team, "Bullet Energy Calculator — Muzzle Energy & Momentum," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/bullet-energy-calculator
@misc{wecalculate_bullet_energy_calculator, title = {Bullet Energy Calculator — Muzzle Energy & Momentum}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/bullet-energy-calculator}}, year = {2026}, note = {TG we-Calculate} }
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