Ballistic Energy & Coefficient Calculator: KE, BC, MOA, and Bullet Drop

The range table produced by the calculator above has six columns: retained velocity (fps), kinetic energy (ft-lbs), bullet drop (inches), bullet drop (MOA), wind drift (inches), wind drift (MOA), and time of flight (seconds). Three callout values are highlighted at the top: muzzle KE in ft-lbs, your entered BC (echoed back alongside the drag model you selected), and drop at 500 yards in MOA. These three numbers give you an immediate sanity check before you read the full table.

Inputs that matter most:

• Muzzle velocity is the single largest variable. Use a chronographed value from your rifle, not the box velocity. Box velocities are typically shot from a 24-inch test barrel and may not match your setup.
• BC and drag model must match. Select G7 if you are running a boat-tail spitzer; select G1 only if the manufacturer provides a G1 figure and you are using it in a G1 solver.
• Zero range sets the reference point for all drop values. A 100-yard zero means the drop column shows how far the bullet is below the 100-yard line of sight at each increment.
• Atmospheric inputs (altitude, temperature, humidity) affect air density and therefore drag. A 5,000-foot DA change can shift your 500-yard drop by 1–2 MOA on a typical .308 load.

Compare Two Loads toggle: enable it to enter a second bullet weight, BC, and muzzle velocity. The table expands to show both loads side by side. This is useful when choosing between two factory loads, evaluating a heavier bullet at reduced velocity, or assessing what a barrel change does to your energy budget.

The MOA column translates directly to scope dial input. The wind drift MOA column gives you a reticle hold if your optic uses MOA subtensions. Both are explained in detail in the MOA section below.

Kinetic energy is the mechanical energy of a moving object. For a bullet, the working form of the equation is:

KE (ft-lbs) = (m × v²) / 450,437

where m is bullet weight in grains and v is velocity in feet per second. The constant 450,437 converts the grain-fps units into foot-pounds. This is equivalent to the standard ½mv² with the appropriate unit conversions applied.

Worked example: A 175 gr Sierra MatchKing at 2,650 fps produces (175 × 2,650²) / 450,437 = (175 × 7,022,500) / 450,437 ≈ 2,728 ft-lbs at the muzzle.

The more important question for practical shooting is energy retention downrange. A bullet sheds velocity as it fights aerodynamic drag. Because KE scales with v², velocity loss compounds into sharper KE loss. Bullets with higher BCs retain velocity longer, which means they retain KE longer.

Consider two loads leaving the muzzle:

• Load A: 55 gr, G7 BC 0.151, 3,300 fps → muzzle KE ~1,330 ft-lbs
• Load B: 175 gr, G7 BC 0.315, 2,600 fps → muzzle KE ~2,624 ft-lbs

At 500 yards, Load B retains roughly 1,600 ft-lbs. Load A may retain only 450–500 ft-lbs depending on conditions. The high-BC, moderate-velocity load does not just start with more energy, it retains proportionally far more of it.

This matters practically for hunters. Many state regulations and accepted field standards require a minimum of 1,000 ft-lbs of retained energy for deer-sized game at the point of impact. The range table lets you find the maximum range at which your load still meets that threshold. Confirming energy-at-range before the hunt is straightforward with the tool above, look down the KE column and find where it drops below your required minimum.

Ballistic coefficient quantifies how efficiently a bullet overcomes aerodynamic drag relative to a standard reference projectile. The formula is BC = SD / i, where SD is sectional density (bullet weight divided by the square of its diameter, in consistent units) and i is the form factor relative to the standard. A higher BC means less drag relative to mass, the bullet retains velocity better.

G1 vs. G7: The G1 standard uses a flat-based, blunt-nosed reference projectile derived from 19th-century Krupp artillery tables. The G7 standard uses a boat-tail spitzer reference that closely resembles modern long-range rifle bullets. For a boat-tail bullet, the G7 drag curve tracks actual deceleration far more accurately across the velocity range from 3,000 fps down through transonic.

A common source of confusion: G7 BC values are numerically roughly half the G1 BC value for the same bullet. This is not because the bullet performs worse, it is because the reference projectiles differ. Example: Hornady 147 gr ELD-M, G1 BC = 0.697, G7 BC = 0.338. Both are correct; they must be used in the matching solver.

Using a G1 BC in a G7 solver (or vice versa) produces errors that compound with distance, errors of several inches at 500 yards and potentially feet at 1,000 yards are possible.

Manufacturer-published BCs are often average values measured at a single velocity or a limited range. BC varies with velocity, especially near transonic. Truing against live-fire data is always preferable to relying on the box number.

Typical G7 BC ranges by bullet weight (rifle, spitzer boat-tail):

| Bullet Weight | Typical G7 BC Range | |---|---| | 55 gr (.224) | 0.140 – 0.175 | | 77 gr (.224) | 0.190 – 0.230 | | 168 gr (.308) | 0.240 – 0.275 | | 175 gr (.308) | 0.290 – 0.330 | | 230 gr (.308) | 0.330 – 0.390 |

Use this table to sanity-check inputs before running the calculator. A G7 BC of 0.600 for a 168 gr .308 bullet is a data-entry error, likely a G1 value entered in the wrong field.

MOA, minute of angle, is an angular unit equal to 1/60th of one degree. At 100 yards, 1 MOA subtends approximately 1.047 inches. Because it is an angular unit, it scales linearly with distance: 1 MOA = 2.094 inches at 200 yards, 5.235 inches at 500 yards, and so on.

Distinguish MOA from MRAD (milliradian): 1 MRAD = 3.438 inches at 100 yards (approximately 3.6 inches is the rounded figure commonly used; precisely it is 3.6 inches at 100 yards when using the 1/10 MRAD click convention). The calculator outputs in MOA; if your optic is MRAD, divide the MOA value by 3.438 to convert, or use Atlas Ballistics which outputs in both units.

Translating the MOA column to scope adjustments: If the table shows 14.2 MOA of drop at 500 yards (100-yard zero), and your turret has ¼-MOA clicks, you need 14.2 / 0.25 = 57 clicks up to dial the correction. Verify your turret tracking is accurate, a turret that tracks 0.23 MOA per click instead of 0.25 MOA will produce consistent errors at distance.

Wind hold example: A 10 mph, 90-degree crosswind on a 175 gr load at 2,650 fps produces approximately 9 MOA of drift at 500 yards. The calculator's wind drift MOA column gives you this number directly. On a MOA reticle, you hold the corresponding hash into the wind. On a MRAD reticle, that same drift is roughly 2.6 MRAD.

Calculated MOA holds are a starting point. Atmospheric variation, barrel temperature, lot-to-lot velocity variation, and actual wind conditions all affect the real-world hold. Confirmed DOPE, drops and holds verified at each distance under known conditions, is what a precision shooter actually relies on for first-round hits. The MOA table here gives you the baseline to build from.

Longer barrels allow more complete combustion and greater gas expansion before the bullet exits the muzzle. This increases velocity, up to a point. Diminishing returns set in, typically past 26–28 inches for most full-power rifle cartridges, where the bore friction begins to offset the marginal pressure gain from additional dwell time.

The approximate rule is 20–30 fps per inch of barrel, but this varies significantly by cartridge, powder burn rate, and charge weight. Slow-burning powders in magnum cases benefit more from barrel length than fast-burning powders in compact cases.

Reference table.308 Winchester, 175 gr (illustrative averages; chrono your own rifle):

| Barrel Length | Approx. MV | |---|---| | 16 inches | ~2,450 fps | | 18 inches | ~2,500 fps | | 20 inches | ~2,550 fps | | 24 inches | ~2,650 fps | | 26 inches | ~2,700 fps |

These are representative figures. Individual rifles will vary by ±50–100 fps depending on chamber dimensions, throat length, and specific load.

KE impact of that velocity spread: Using the calculator formula:

• 175 gr at 2,450 fps → KE = (175 × 6,002,500) / 450,437 ≈ 2,334 ft-lbs
• 175 gr at 2,650 fps → KE ≈ 2,728 ft-lbs

That is nearly 400 ft-lbs difference at the muzzle, and the gap widens at distance because the higher-velocity round stays above transonic longer. For a hunter using a 16-inch suppressor host, that energy deficit is real and affects maximum ethical range calculations.

The calculator on this page uses the muzzle velocity you enter directly. The barrel length field provides informational context and displays the reference table, it does not auto-calculate MV from barrel length, because powder charge and cartridge are too variable for that to be reliable. Chrono your actual load and enter the measured value.

The Compare Two Loads toggle in the calculator above adds a second input row for bullet weight, BC, drag model, and muzzle velocity. Both loads share the same atmospheric inputs and zero. The output table displays them side by side at each range increment, allowing direct comparison of retained velocity, KE, drop, and wind drift.

Practical use cases:

• Comparing factory loads before buying in bulk (Federal Gold Medal 168 gr vs. Hornady 175 gr ELD-M for a PRS shooter)
• Evaluating a bullet weight change for hunting to confirm energy minimums at max range
• Assessing what a barrel length change does to your full trajectory, enter the same load at two different MV values reflecting the two barrel lengths

Concrete example: Load A, 168 gr, G7 BC 0.274, 2,650 fps. Load B, 175 gr, G7 BC 0.315, 2,600 fps.

At the muzzle, Load A has approximately 2,624 ft-lbs and Load B approximately 2,624 ft-lbs (nearly identical). At 500 yards, Load B retains more velocity because its higher BC resists drag more effectively. It also drifts less in a crosswind, roughly 0.5–1 MOA less drift at 500 yards in a 10 mph crosswind, depending on conditions. For a PRS shooter making stage calls or a hunter confirming energy retention, Load B is the better selection despite identical muzzle energy and slightly lower muzzle velocity.

This is the core reason muzzle KE alone is a poor metric for long-range load selection. BC governs what happens downrange. Two loads with identical muzzle KE but different BCs diverge significantly past 300 yards in both trajectory and wind sensitivity. The comparison table makes this visible in a format you can evaluate before going to the range.

The calculator on this page uses a point-mass model. It is accurate enough for planning and initial DOPE estimation. It is not a full firing solution for precision long-range work. Here is what it does not account for:

Spin drift: A right-hand-twist barrel imparts clockwise spin, which causes the bullet to drift right (for a right-hand twist) due to gyroscopic precession. At 1,000 yards, spin drift on a typical .308 load can exceed 10 inches, roughly 1 MOA, and is entirely absent from a point-mass calculation.

Coriolis effect: Earth's rotation deflects projectiles laterally and vertically depending on latitude, azimuth, and range. This effect becomes meaningful past approximately 600–800 yards at mid to high latitudes. A point-mass solver ignores it.

Aerodynamic jump: A crosswind that begins before the bullet exits the muzzle imparts a vertical displacement, aero jump, orthogonal to the wind direction. This is small but nonzero and is not modeled here.

Shooter cant: Canting the rifle rolls the bullet's drop vector, converting pure elevation error into a combination of elevation and windage error. The calculator assumes a level rifle.

BC accuracy: Manufacturer BCs are often measured at one velocity and one atmospheric condition. Your bullet, in your rifle, at your altitude, may have a meaningfully different effective BC. Truing corrects for this: shoot at a known distance (500 yards is practical) in calm conditions, measure actual drop, then adjust the BC in your solver until the calculated drop matches the observed drop. That adjusted BC is your trued BC for that load in those conditions.

Atlas Ballistics for iOS includes a built-in truing workflow, shot logging, and DOPE card storage, the tools required to move from a calculated estimate to a confirmed firing solution you can rely on at distance.