Bullet Energy Calculator — Muzzle Energy & Downrange
Compute bullet energy in ft-lbs and joules from bullet weight (grains) and muzzle velocity (fps). Then estimate downrange energy at any distance using the ballistic coefficient. Pure physics — kinetic energy of a projectile.
Muzzle Energy Calculator
Downrange Energy Calculator
Estimate model: v(d) = v₀ · e^(−d / (2700 · BC)) with d in yards, then E = ½mv² from the remaining velocity. Simplified drag model for education — real ballistics uses measured drag curves (G1/G7) and air density.
Bullet Energy Comparison Chart
Typical factory loads — approximate muzzle energy. Tap a row to load it into the calculator.
| Caliber / load | Weight (gr) | Velocity (fps) | Energy (ft-lbs) | Energy (J) | |
|---|---|---|---|---|---|
| .22 LR | 40 | 1200 | 127.9 | 173.5 | |
| .380 ACP | 95 | 980 | 202.6 | 274.7 | |
| 9mm Luger | 115 | 1180 | 355.6 | 482.2 | |
| .40 S&W | 180 | 1000 | 399.8 | 542.0 | |
| .45 ACP | 230 | 850 | 369.1 | 500.4 | |
| .357 Magnum | 158 | 1250 | 548.3 | 743.4 | |
| .44 Magnum | 240 | 1350 | 971.5 | 1317.2 | |
| 7.62×39mm | 123 | 2350 | 1508.7 | 2045.5 | |
| .223 Rem | 55 | 3200 | 1250.9 | 1696.0 | |
| .243 Win | 100 | 2960 | 1946.0 | 2638.4 | |
| 6.5 Creedmoor | 140 | 2700 | 2266.8 | 3073.4 | |
| .270 Win | 130 | 3060 | 2703.6 | 3665.6 | |
| .308 Win | 150 | 2820 | 2649.4 | 3592.1 | |
| .30-06 Springfield | 180 | 2750 | 3023.4 | 4099.2 | |
| 12 ga slug (1 oz) | 438 | 1600 | 2490.4 | 3376.5 | |
| .50 BMG | 660 | 2950 | 12756.9 | 17296.0 |
Values are typical factory-load approximations computed with the same formula — actual ammunition varies by manufacturer and barrel length.
The Muzzle Energy Formula
Energy (ft-lbs) = (bullet weight in grains × velocity in fps²) ÷ 450240
Energy (joules) = ½ × mass in kg × velocity in m/s²
Conversions: 1 grain = 64.79891 mg (0.06479891 g). 1 fps = 0.3048 m/s. 1 ft-lb = 1.3558 joules. Because velocity is squared, a small increase in muzzle velocity raises bullet energy far more than the same proportional increase in bullet weight — this is why light, fast projectiles can carry surprising energy.
Frequently Asked Questions
What is the muzzle energy formula?
Bullet kinetic energy follows the physics formula E = 1/2 m v². With bullet weight in grains and velocity in fps, the practical formula is: Energy (ft-lbs) = (bullet weight in grains × velocity in fps²) / 450240.
How do you calculate bullet energy in ft-lbs?
Multiply the bullet weight in grains by the square of the muzzle velocity in fps, then divide by 450240. Example: a 115 grain bullet at 1180 fps gives (115 × 1180 × 1180) / 450240 ≈ 355.6 ft-lbs.
How do I convert ft-lbs to joules?
Multiply ft-lbs by 1.3558 to get joules. Conversely, divide joules by 1.3558 to get ft-lbs. For example, 355.6 ft-lbs equals about 482 joules.
How do you calculate bullet energy in joules directly?
Use E = 1/2 m v² with mass in kilograms and velocity in meters per second. Convert grains to kg (1 grain = 64.79891 mg) and fps to m/s (1 fps = 0.3048 m/s), then the result is in joules.
Does bullet energy depend more on velocity or weight?
Velocity matters more, because energy scales with the square of velocity but only linearly with mass. Doubling velocity quadruples energy, while doubling bullet weight only doubles it.
What is the difference between muzzle energy and muzzle velocity?
Muzzle velocity is how fast the bullet leaves the barrel (fps or m/s). Muzzle energy combines that speed with the bullet's mass to measure kinetic energy (ft-lbs or joules). Two bullets with the same velocity but different weights have different energies.
How is downrange bullet energy calculated with ballistic coefficient?
A ballistic coefficient (BC) describes how well a bullet resists air drag. This calculator estimates velocity decay with v(d) = v₀ × e^(−d / (2700 × BC)), where d is distance in yards, then computes kinetic energy from the remaining velocity. It is an estimate, not a substitute for measured ballistic data.
What is energy retention downrange?
Energy retention is the percentage of muzzle energy a bullet still carries at a given distance. High-BC bullets shed velocity slowly and retain more energy; low-BC bullets lose energy quickly to air drag.
What is the muzzle energy of 9mm Luger?
A typical 115 grain 9mm load at 1180 fps produces about 355.6 ft-lbs (482.2 joules) of muzzle energy. A heavier 147 grain load at 990 fps produces about 320 ft-lbs (434 joules).
What is the muzzle energy of .223 Remington?
A typical 55 grain .223 Remington load at 3200 fps produces about 1250.9 ft-lbs (1696.2 joules) of muzzle energy.
What is the muzzle energy of .308 Winchester?
A typical 150 grain .308 Winchester load at 2820 fps produces about 2649.4 ft-lbs (3592.1 joules) of muzzle energy.
What is the muzzle energy of .22 LR?
A typical 40 grain .22 LR load at 1200 fps produces about 127.9 ft-lbs (173.5 joules) of muzzle energy, much less than centerfire rifle cartridges.
Is muzzle energy the only measure of a bullet's effectiveness?
No. Muzzle energy is one physics quantity among many. Real-world effectiveness also involves bullet construction, penetration, shot placement, and other factors this educational calculator does not model.
Why do downrange energy estimates vary between calculators?
Because air drag depends on the bullet's shape, the drag model (G1 vs G7), air density, and velocity. Simple exponential-decay models like this one are estimates; professional ballistic solvers integrate measured drag curves for each bullet.
Can I use this calculator for airguns or archery?
Yes. The kinetic energy formula E = 1/2 m v² applies to any projectile. Enter the projectile weight in grains (1 gram = 15.432 grains) and velocity in fps to get energy in ft-lbs and joules.
Is this calculator shooting or reloading advice?
No. This is an educational physics tool for learning how kinetic energy, mass, velocity, and ballistic coefficient relate. It provides no instructions for firearms, ammunition, reloading, or shooting, and nothing here should be treated as shooting guidance.