Arrow Ballistics Calculator

Arrow Ballistics & FOC Calculator

Results:

Kinetic Energy: 0 ft-lbs

Momentum: 0 slug-ft/s

FOC (Front of Center): 0%

Ethical Game Size: N/A

function calculateArrowBallistics() { var weight = parseFloat(document.getElementById('arrowWeight').value); var velocity = parseFloat(document.getElementById('arrowVelocity').value); var length = parseFloat(document.getElementById('arrowLength').value); var balance = parseFloat(document.getElementById('balancePoint').value); if (isNaN(weight) || isNaN(velocity) || isNaN(length) || isNaN(balance) || weight <= 0 || velocity <= 0 || length <= 0) { alert("Please enter valid positive numbers for all fields."); return; } // KE = (Weight * Velocity^2) / 450240 var ke = (weight * Math.pow(velocity, 2)) / 450240; // Momentum = (Weight * Velocity) / 225218 var momentum = (weight * velocity) / 225218; // FOC = (100 * (A – L/2)) / L // A = distance from nock to balance point // L = total length var foc = (100 * (balance – (length / 2))) / length; document.getElementById('resKE').innerText = ke.toFixed(2); document.getElementById('resMom').innerText = momentum.toFixed(3); document.getElementById('resFOC').innerText = foc.toFixed(2); var gameRecommendation = ""; if (ke = 25 && ke = 42 && ke < 65) { gameRecommendation = "Large Game (Elk, Black Bear)"; } else { gameRecommendation = "Tough Game (Moose, Buffalo)"; } document.getElementById('resGame').innerText = gameRecommendation; document.getElementById('ballistics-results').style.display = 'block'; }

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Understanding Arrow Ballistics: KE, Momentum, and FOC

When fine-tuning your archery setup, whether for target shooting or ethical bowhunting, understanding the physics behind your arrow flight is crucial. This calculator provides the three most critical metrics for performance: Kinetic Energy (KE), Momentum, and Front of Center (FOC).

Kinetic Energy vs. Momentum

Many archers confuse Kinetic Energy with Momentum. While KE is the total energy your arrow carries (useful for breaking bones), Momentum is the measure of the arrow's ability to stay in motion when it meets resistance. In bowhunting, momentum is often considered a better predictor of deep penetration than KE alone.

The Importance of FOC (Front of Center)

FOC describes what percentage of the arrow's weight is located in the front half of the arrow. A higher FOC generally leads to more stable flight, especially at long distances or in windy conditions. Most bowhunters aim for an FOC between 10% and 15%, though heavy-hitting "Extreme FOC" setups can exceed 19%.

Standard Performance Benchmarks

Game Type	Kinetic Energy (ft-lbs)
Small Game (Rabbit/Turkey)	< 25 ft-lbs
Medium Game (Whitetail/Antelope)	25 – 41 ft-lbs
Large Game (Elk/Wild Boar)	42 – 65 ft-lbs
Dangerous/Big Game (Buffalo/Grizzly)	> 65 ft-lbs

Practical Example

If you shoot a 450-grain arrow at 280 fps:

• Kinetic Energy: (450 * 280^2) / 450,240 = 78.36 ft-lbs
• Momentum: (450 * 280) / 225,218 = 0.559 slug-ft/s

This setup would be more than sufficient for even the largest North American game animals. By adjusting your point weight or arrow shaft length, you can use this calculator to find the "sweet spot" for your specific bow and target goals.