Can I use my phone to read greens or look up info during a round?

You can use your phone for basic distance and weather info, but not to read greens with detailed maps, measure elevation changes, or get live club recommendations based on your current round. Rule 4.3 allows pre-round notes and distance devices, but bans anything that replaces the skill of reading a green or judging a shot.

What your phone can do

A phone is just equipment, so Rule 4.3 treats it like any other device. You may use it to check yardages from a distance-measuring app, look at a compass for direction, or pull up a weather forecast for wind speed, temperature, and humidity. You can also view notes, yardage books, or swing tips you prepared before the round started. Recording stats like club distances or your heart rate for later review is fine too.

What your phone cannot do

You cannot use an app that shows detailed green contours, heat maps, or a recommended putt line — those are electronic green-reading materials limited by Interpretation 4.3a/1. You also cannot measure elevation changes or use the phone as a level to gauge slope. Processing live data from your round — such as an app that suggests a club based on how far you've actually hit it today — is prohibited. Measuring wind speed at the course with the phone's sensors or using powder, a ribbon, or any artificial aid to judge wind is also not allowed.

The green-reading limit

Interpretation 4.3a/1 caps the size and scale of any putting-green map, paper or digital, that you consult during the round. A committee can go further with Model Local Rule G-12 and ban all green-reading materials entirely. So even if your phone app shows a simplified green diagram, check whether the competition has adopted G-12 before you open it on the putting surface.

Exceptions that change the answer

• The Committee adopts Model Local Rule G-5 → All distance-measuring devices, including phone apps, may be prohibited for the competition.
• The Committee adopts Model Local Rule G-12 → No green-reading materials of any kind — paper or electronic — may be used during the round.
• You use the phone purely as a club (e.g., as a plumb bob) → Holding the phone vertically to help judge slope is allowed, just like using a club as a plumb line. But placing it on the green as a level or using a bubble-level app is not.

Frequently asked questions

Can I check the elevation change to the green on my phone?

No. Rule 4.3a(1) explicitly prohibits measuring elevation changes, whether with a phone, a rangefinder, or any other device.

Can I look up a club recommendation based on my shots today?

No. Processing or interpreting playing information from the current round — such as club suggestions based on your actual distances today — is prohibited under Rule 4.3a(3). Pre-round notes are fine; live analysis is not.

Can I use my phone's weather app for wind speed on the course?

You can check a general weather forecast on your phone, but you cannot measure wind speed at the course using the phone's sensors or any artificial aid like powder or a ribbon. Rule 4.3a(2) allows forecast data only.

What's the penalty if I break Rule 4.3 with my phone?

First breach: two penalty strokes (or loss of hole in match play). Second breach: disqualification. The penalty applies even if you didn't actually gain an advantage — the rule targets the potential advantage created by the prohibited use.