Bullet Impact Energy Calculator

Calculator

Projectile mass

kggmggrainozlb

Tip: grain is common for small masses. Values must be positive.

Impact velocity

m/skm/hft/smph

Velocity should reflect the moment of impact.

Impact angle (optional)

degrees

0° means straight impact. 90° means full glancing.

Energy transfer estimate (optional)

%

This is a rough parameter for material or capture effects.

Load example data

Choose an example… Sample A — 115 grain, 1200 ft/s Sample B — 55 grain, 3200 ft/s Sample C — 147 grain, 2600 ft/s Sample D — 40 grain, 1500 ft/s Sample E — 10 grain, 900 ft/s Sample F — 62 grain, 1100 ft/s Sample G — 180 grain, 950 ft/s Sample H — 90 grain, 2000 ft/s Sample I — 230 grain, 850 ft/s Sample J — 36 grain, 1400 ft/s Load

Loading an example will overwrite current inputs.

Calculate Download CSV Download PDF Reset

This tool reports physical energy values only. Use results responsibly and legally.

Results

Enter values above and click Calculate to see results.

Formula Used

Total kinetic energy:

E = ½ · m · v²

• E is energy in joules (J).
• m is mass in kilograms (kg).
• v is impact velocity in meters per second (m/s).

Angle split (optional):

vₙ = v · cos(θ),   vₜ = v · sin(θ)

Eₙ = ½ · m · vₙ²,   Eₜ = ½ · m · vₜ²

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Unit conversions are handled automatically. For reference: 1 J = 0.737562149 ft·lbf.

How to Use This Calculator

1. Enter the projectile mass and choose its unit.
2. Enter the impact velocity and choose its unit.
3. Optionally add an impact angle between 0° and 90°.
4. Optionally set an energy transfer percentage.
5. Click Calculate to view joules and ft·lbf.
6. Use Download CSV or Download PDF to save results.

Bullet Impact Energy Guide

Impact energy is the kinetic energy carried at the moment of contact. This calculator uses mass and impact velocity to compute energy in joules, plus a foot‑pound equivalent. It can also estimate transferred energy using a percentage setting. For example, 115 grain at 1200 ft/s produces about 498 J (≈368 ft·lbf).

Inputs that matter most

The two dominant variables are mass and velocity, but velocity influences energy quadratically. Doubling velocity makes energy four times larger, while doubling mass only doubles energy. If your chronograph or sensor data varies by 5%, your energy result can vary by roughly 10%. Use impact velocity, not muzzle velocity, if drag or distance is significant.

Unit choices and quick conversions

Choose the unit that matches your measurements and let the calculator convert internally to kilograms and meters per second. Helpful anchors: 1 grain = 0.0648 g, 1 ft/s = 0.3048 m/s, and 1 mph = 0.44704 m/s. Consistent units reduce mistakes when comparing test sets. The example selector can preload common mass and speed pairs for quick checks.

Reading joules and foot‑pounds

Joules are the standard physics unit, while foot‑pounds are often used in English‑unit reporting. The tool converts using 1 J = 0.73756 ft·lbf. If you export a PDF, both units are included so you can share results across labs, classrooms, and spreadsheets.

Angle: straight vs glancing impact

Angle is optional, but it adds insight. The calculator splits velocity into a normal component vₙ and tangential component vₜ using cosine and sine. At 45°, total energy stays the same, yet normal energy and tangential energy become equal. A 15° strike keeps most energy in the normal direction. This helps compare straight and glancing impacts.

Energy transfer as a practical estimate

Materials, deformation, and capture effects determine how much energy actually transfers to the target. The transfer percentage is a simple knob: 100% assumes full transfer, while 40% suggests substantial retained motion or fragmentation losses. It is not a prediction model, but it helps bracket scenarios. Keep the chosen percentage consistent when reporting results.

Interpreting results and common ranges

Use the results to compare setups, validate measurements, and communicate assumptions. Typical small‑mass cases may be tens to hundreds of joules, while high‑velocity cases can reach several thousand joules. Always record the same distance, conditions, and measurement method when building a dataset. Export CSV to keep a consistent log for later review in reports.

FAQs

What does this calculator compute?

It computes kinetic energy from mass and impact velocity, reporting joules and foot‑pounds. If you add an angle, it also shows normal and tangential energy components for straight versus glancing impacts.

Which velocity should I enter?

Use the best estimate of velocity at the moment of impact. If distance and drag are meaningful, do not use muzzle velocity. A measured downrange or impact‑adjacent value will give more realistic energy results.

Why does velocity change energy so much?

Energy scales with v², so small velocity changes have a big effect. For example, a 10% increase in velocity raises energy by about 21%, while a 10% increase in mass raises energy by 10%.

What does “energy transfer %” mean?

It is a simple way to estimate how much of the calculated energy is delivered to the target. Set 100% for a full transfer assumption, or lower values to represent retained motion, deflection, or fragmentation.

Can I use grains and ft/s directly?

Yes. Select grain for mass and ft/s for velocity, then calculate. The tool converts internally to kilograms and meters per second, ensuring the physics formula stays consistent while you keep familiar units.

How do I save my results?

After calculating, use Download CSV to store a running history in a spreadsheet, or Download PDF to save a one‑page report of the latest result. The CSV keeps up to 50 recent entries.