How do golf rangefinders work?

Time of flight: the basic method

When you press the button, the rangefinder sends out a rapid series of short, invisible infrared laser pulses. Some of the light bounces off the target and returns to a sensor in the device. A precise clock measures the round trip time. Since light travels at a known, very high speed, the device can turn that tiny time into a distance, then display it in yards or metres.

Because the pulses are so short and the timing so precise, golf rangefinders can measure to within about a yard, and makers often quote figures such as plus or minus half a yard. Range depends on how well the target reflects: trees and buildings reflect well, flags less so, which is why makers quote a shorter range to a flag.

First target priority and pin seeking

The laser beam spreads slightly as it travels, so at 150 yards it can hit the flag and the trees behind it. The sensor receives several echoes. Golf rangefinders use first target priority: they report the nearest echo, which is usually the flag. Pin seeking features refine this, and many models vibrate or flash to confirm they have locked on to the nearer target. Bushnell calls its version JOLT.

This is the main difference from hunting rangefinders, which often favour the farthest target; see golf rangefinder vs hunting rangefinder.

Scan mode

Holding the button down usually puts the rangefinder in scan mode, where it updates the reading continuously as you move it. That lets you sweep across bunkers, trees and the flag to see several distances, and helps lock on to a flag if your hands move. How to hold a rangefinder steady has technique tips.

How slope works

Slope models add an inclinometer that measures the angle up or down to the target. The device knows the straight line distance and the angle, so it can calculate the horizontal distance and the height difference with simple trigonometry. Makers then apply their own formula to suggest a plays like distance, which is why slope figures differ between brands.

Our rangefinder maths tool shows the geometry, and how slope adjusted yardage works explains it in detail. Under Rule 4.3 of the Rules of Golf, published by The R&A, slope must not be used in a competition round.

Why a reading can be wrong

Most wrong readings come from the beam hitting something other than the flag: the trees behind, a bank in front or rain and mist in between. Very bright sun can make the display harder to read, and a low battery can slow or stop readings. The fix is usually technique and settings rather than a fault.

Magnification and display

Most golf lasers use 6x magnification. That makes the flag look six times closer while keeping a wide enough view to find the target. Displays are either black LCD or lit red or dual colour displays that are easier to read in low light. If the display shows metres, see how to change a rangefinder to yards.

See golf rangefinders compared →

Safety

Golf rangefinders use low power lasers classed as safe for normal use, but you should still follow the maker's safety instructions. Do not look at the sun through the eyepiece and do not aim the laser at people's eyes.

Note:Never look at the sun through a rangefinder or point it at anyone's eyes.

Frequently asked questions

How accurate are golf rangefinders? Most quote accuracy within about a yard to a clear target. Technique matters more than the stated figure.

Where should I aim my rangefinder? Aim at the flagstick, ideally the flag cloth or upper stick, and scan across it until the device confirms a lock.

Do rangefinders work in rain? Usually, but heavy rain and mist can scatter the beam and reduce range.