Calculate Crossbow Efficiency

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This calculator is pre-loaded with Bunjie, Jr.’s specs so you can see how your crossbow compares!

Find out how efficient your crossbow is (or any crossbow) by entering accurate data to get a pretty good estimate. Crossbow efficiency isn't talked about very much, but it's quite important. This is a measurement of how much energy your crossbow stores when it is cocked, and how much it delivers to your arrow when you pull the trigger. The higher the percentage of efficiency, the better—more efficiency means more energy imparted on the arrow, and less energy left over. Leftover energy is wasted, dumped into the limbs and riser and scope, and creates sound and heat. More leftover energy means more potential damages to strings, limbs, and other parts.

Naturally, this is not everything that affects the performance and longevity of your crossbow, but this is a fun way to see how YOUR crossbow performs with different arrow weights, and how one crossbow performs against another crossbow. You will need your power stroke (the distance from the string at rest to the trigger latch—basically the distance the string travels from the cocked to uncocked position). You’ll also need your crossbow’s draw weight (not draw effort—which changes with the device used to cock the crossbow—we need the draw weight).

Perhaps the most important figure above isn’t the percentage of efficiency, but how much energy is left over! That’s how much energy our crossbows waste—energy that create noise and damage crossbows over time!

For comparisons, the Original Bunjie is only around 35% efficient with stock arrows, but Bunjie III is over 60% efficient with its current arrow setup! Modern compound vertical bows might be in the 60’s, also, for comparison’s sake.

More efficient crossbows may last longer (think broken limbs), be quieter, and might be more comfortable and even more accurate to shoot (think Bunjie III). Less efficient crossbows will be louder, and might suffer from loose bolts and broken parts with more frequency (think Bunjie, Jr., hovering around 40% efficiency). That’s not a guarantee! Remember, there are no guarantees in this business! (I say that a lot, don’t I?) Remember, the Original Bunjie is a very inefficient crossbow, but has never struggled with accuracy or broken parts. The O.B. would happily go kill a bear today! This is just one more topic of conversation, one more thing to consider about crossbow designs!