The most common way to measure arrow speed is with a chronograph, a device that clocks your arrow as it passes through or past a unit positioned a few feet in front of your bow. Chronographs come in two main types, optical and radar, and both give you a reading in feet per second (FPS). There are also smartphone apps that estimate speed using sound, though they’re less precise. Here’s how each method works and what affects your results.
Optical Chronographs
Optical chronographs use two light sensors spaced a known distance apart. As your arrow passes over the first sensor it triggers a timer, and when it crosses the second sensor the timer stops. The device divides the distance between sensors by that elapsed time and displays your speed in FPS.
These units typically cost $100 to $200 and are straightforward to use. You place the chronograph on a table or stand a few feet in front of your bow, line up your shot so the arrow flies directly over the sensors, and shoot. Most archers position the unit about 3 to 6 feet from the riser to capture speed close to the bow.
The main drawback is lighting sensitivity. Direct sunlight, passing shadows, and indoor fluorescent lighting can all cause inconsistent or outright wrong readings. Fluorescent bulbs flicker at a frequency that can interfere with the sensors, so if you’re shooting indoors under fluorescents, expect some erratic numbers. Overcast outdoor light or consistent artificial light (LED, incandescent) tends to produce the most reliable results. Even with good lighting, optical chronographs are generally considered less reliable for archery than radar units, partly because arrows are slower and thinner than bullets, which is what most optical chronographs were originally designed to measure.
Radar Chronographs
Radar chronographs emit a continuous microwave signal and detect the Doppler shift as an object moves through the beam. Because they don’t rely on light, they’re far less affected by environmental conditions. Readings are more consistent and generally more accurate than optical models.
The biggest advantage for archers is that some radar units, like the LabRadar, can track your arrow’s speed at multiple distances downrange, not just at the device itself. That means you can see how quickly your arrow decelerates over 10, 20, or 30 yards, which is valuable for tuning setups or comparing broadhead performance. You place the unit beside you at the shooting line rather than downrange, so there’s no risk of damaging it with a stray shot.
The tradeoff is cost. Radar chronographs run $300 to $600 or more, which puts them out of casual territory. For serious bowhunters and competitive archers who test multiple setups, the investment pays off in reliability and data depth. For someone who just wants a one-time speed check, it’s harder to justify.
Smartphone Sound-Based Apps
A newer, budget-friendly option uses your phone’s microphone to estimate arrow speed. These apps work by detecting two distinct sounds: the release of the arrow from the bow and the impact of the arrow hitting the target. The app measures the time between those two audio events. You then enter the distance from your phone to the archer and the distance from the archer to the target, and the app factors in the speed of sound to calculate your arrow’s average speed over that distance.
This method is clever but introduces several variables. Background noise, wind, and even how cleanly the arrow hits the target can affect the accuracy of the sound detection. The result is an average speed across the full flight, not launch speed, so it will read lower than a chronograph placed near the bow. It’s a reasonable ballpark tool if you don’t have access to a chronograph, but don’t rely on it for precise tuning.
What the Speed Ratings on Your Bow Mean
Bow manufacturers advertise speed ratings using standardized testing protocols, and those numbers are always higher than what you’ll see in real-world shooting. The two main standards are IBO and ATA.
IBO speed is measured at 80 pounds of draw weight (plus or minus 2 pounds), maximum draw length for that bow, and a 400-grain arrow. ATA speed uses 70 pounds of draw weight (plus or minus 0.2 pounds), a fixed 30-inch draw length, and a 350-grain arrow. Because the ATA protocol uses less draw weight and a lighter arrow at a standardized draw length, while IBO maximizes the bow’s potential, these two ratings for the same bow can differ noticeably.
Your actual speed will almost certainly be lower than either rating. If you shoot at 60 pounds with a 28-inch draw and a 450-grain arrow, you’re giving up energy at every variable. The advertised number is a controlled ceiling, useful for comparing one bow to another but not a prediction of your personal setup’s performance. That’s exactly why measuring your own arrow speed matters.
Tips for Getting Accurate Readings
Whichever method you use, consistency is key. Shoot at least five arrows through the chronograph and average the results. If one reading is wildly different from the others (more than 5 FPS off), throw it out and shoot again. A well-tuned bow with consistent form should produce readings within 2 to 3 FPS of each other.
If you’re using an optical chronograph, control your lighting. Shoot on an overcast day or under steady, non-fluorescent artificial light. Keep the sensors out of direct sun, and avoid setups where your body casts a moving shadow over the unit as you draw. Position the chronograph so the arrow passes squarely over both sensors at the same height; an angled flight path can slightly skew the reading.
For radar units, make sure the device is level with and beside your bow at the shooting line. Most radar chronographs need a clear line of detection along the arrow’s flight path, so avoid placing anything between the unit and the target that could reflect the signal. Follow the manufacturer’s recommended distance from the bow, which is usually within a foot or two of the riser.
Temperature also plays a role. Cold weather stiffens limbs and string materials, which can reduce speed by several FPS compared to warm conditions. If you’re measuring in winter, expect lower numbers than a summer session with the same setup.
What to Do With Your Speed Number
Once you have a reliable FPS reading, you can calculate kinetic energy, which tells you how much force your arrow delivers on impact. The formula is simple: multiply the arrow’s weight in grains by the speed in FPS squared, then divide by 450,436. The result is foot-pounds of kinetic energy. For example, a 400-grain arrow traveling at 280 FPS produces about 69.6 foot-pounds.
Kinetic energy matters for bowhunters choosing setups for different game. Most experienced hunters aim for at least 40 to 45 foot-pounds for whitetail deer and 55 to 65 foot-pounds for elk-sized animals. Knowing your actual speed, not the number on the bow’s spec sheet, lets you make informed decisions about arrow weight, broadhead choice, and whether your setup has enough energy for the hunt you’re planning.
Speed also directly affects arrow trajectory. Faster arrows fly flatter, which means less pin gap between your sight pins at different distances. If you’re setting up a new sight or switching to a heavier broadhead, re-measuring your speed gives you the real number to plug into ballistic calculators or sight tapes instead of guessing.