Morris on the gadgets
Are golf rangefinders legal? What Rule 4.3 allows
A rangefinder is allowed; a rangefinder with the slope switch on is not, in a competition. The line between information and advice is thin, so here is exactly where the Rules draw it for rangefinders, GPS watches and apps.
A rules or etiquette question on the course?
Ask MorrisBy Morris, by Badgie Golf · Updated
What you can and cannot do in a competition
| What the device does | Allowed? |
|---|---|
| Distance to the flag or a hazard | Yes |
| Direction information, a compass | Yes |
| Elevation change (slope) | No |
| Recommends a club or a line | No |
| Measures wind speed on the course | No |
| Weather forecast, temperature and humidity | Yes |
| Alignment aid to line up the ball | No |
Information versus advice
The Rules do not care what the device is called. A laser rangefinder, a GPS watch and a phone app are all distance-measuring devices, and the question is what they do with the information. Showing 143 yards to the middle of the green is information. Subtracting 6 yards for the uphill and telling you to hit a 7-iron is interpretation, and the Rules do not allow it in a competition round.
That includes smart caddies and AI tools: ask them about clubs and lines before the round, on the range or in practice, and switch them off for a competition. Morris, for example, belongs to the practice side of the game: it analyses your swing on video and answers questions about the Rules.
Before you tee off
Read the scorecard and the notice board for a Local Rule on distance-measuring devices; clubs that ban them say so there. If your rangefinder has a slope switch, turn it off or use the tournament-legal setting. If you are unsure, ask the Committee before you start. For the rest of the rules you will meet on the course, see golf rules explained, and for the apps themselves the best golf GPS app.
Sources
- The R&A — Rules of Golf, Rule 4: Player's Equipment — Rule 4.3a: distance-measuring devices, elevation, interpreting information, wind speed, Model Local Rule G-5 and the penalty. Read 18 October 2026.
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Questions about rangefinders and the Rules
Are rangefinders allowed in golf competitions?
Yes, by default. Rule 4.3a lets you get distance or direction information from a distance-measuring device. The exception is a Local Rule: the Committee may adopt Model Local Rule G-5 and ban distance-measuring devices altogether, so check the notice board or the scorecard before the round.
Can I use the slope function of my rangefinder in a competition?
No. Measuring elevation changes, the Rules' word for slope, is not allowed in a competition round. Many rangefinders have a switch or a tournament-legal version for exactly this reason. In a friendly round nobody enforces it, so use slope there if you like.
Can my golf app tell me which club to hit?
Not in a competition round. Rule 4.3a does not allow a device to interpret distance or direction information, for example to recommend a club or a line. An app that only shows yards to the front, middle and back of the green is giving information; one that says take a 7-iron is interpreting it.
Can I check the wind speed or the weather?
You may look at weather forecasts and measure temperature and humidity at the course. You may not measure wind speed at the course. A flag, a tree or a blade of grass is not a device, so what you see is free.
What happens if I break Rule 4.3 by mistake?
The first breach is the general penalty, which is two strokes in stroke play and the loss of the hole in match play. A second breach, after an intervening event, is disqualification. The cure is simple: switch the slope function off and ask before the round.
Is a GPS watch a distance-measuring device?
Yes, a GPS watch or phone app that shows yardage works as a distance-measuring device in the Rules, so the same limits apply: distance is fine, slope readings and club recommendations are not in a competition round.
The rules, when you need them
Send him your situation as it is, where the ball lies and what happened, and he tells you the rule and how to play on.
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