Calculate arrow kinetic energy in foot-pounds and joules from arrow weight in grains and speed in fps, or solve for the arrow weight or speed.
Arrow Kinetic Energy Formula
Kinetic energy depends linearly on mass and on the square of speed. Use finished arrow mass and a measured launch speed for the most useful result.
How the Calculation Works
Choose the requested output and enter the visible source values. Unit changes convert the current quantity; switching modes retains entered values.
How to Use This Calculator
- Select the value or workflow you want in the Solve for menu.
- Enter only the visible source values and use the units shown beside them.
- Select Calculate and review the primary answer, supporting values, warning, and steps.
- Use Reset before starting a different bow, arrow, or round.
Worked Example
A 450-grain arrow at 280 fps carries about 78.324 ft-lbf, or 106.193 joules, using SI-consistent conversions. The customary 450240 divisor is an approximation.
Input and Result Guide
| Item | How to use it |
|---|---|
| Arrow weight | Use the complete finished arrow, including every installed component. |
| Speed | Prefer a chronograph measurement from the actual bow and arrow. |
| Energy | The calculator reports both foot-pounds-force and joules. |
| Inverse modes | Choose the output unit before entering the other two source values. |
| Hunting decisions | Check current jurisdiction rules and equipment-maker requirements directly. |
Interpreting the Result
Because velocity is squared, a small speed change affects energy more than the same percentage change in arrow mass. Energy alone does not describe broadhead design, tune, placement, or penetration.
Assumptions and Limitations
There is no universal game-animal kinetic-energy threshold. Do not use an estimated bow speed when a measured value is needed for legal or equipment decisions.
Common Questions
Why did a field disappear after I changed Solve for?
A hidden field is either the requested output or irrelevant to the selected workflow. Enter the remaining visible source values.
Will my last successful calculation be restored?
Yes. Successful source inputs are saved in this browser and the result is recomputed when restored. Reset clears that saved state.
Sources
Easton Archery, arrow kinetic-energy method; NIST unit-conversion constants; current jurisdiction hunting regulations.
