Golf green reader for iPhone
Your phone is the plumb line.
Plumb Bob scans the green with your camera, measures the slope and draws the line, the aim point and the break right on the grass. Read every putt like a tour caddie.
3 free reads · No account · Works offline
- Aim9.6 in left
- Break2 cups out
- Plays like12 ft
- Green speedStimp 10.5
How it works
Ball. Hole. Plumb.
The same walk you already take to read a putt. About twenty seconds, then you putt.
- 01Mark your ballStand beside it and tap. Plumb Bob finds the ball on the green.
- 02Mark the cupWalk your line to the hole and aim at the cup. The walk scans the slope under your putt.
- 03Plumb itStand behind the ball and hold the phone up. A truly vertical line runs through the ball, the cup shows on the side it breaks, and your line appears on the grass.
Why it works
The oldest read in golf, done right.
Plumb bobbing is how golfers have read greens for a century: hang the putter shaft in front of your eye, line it up with the ball, and see which side the hole falls on. It only works if the shaft is truly vertical, you stand square to the slope, and the slope doesn't change between you and the hole. It rarely all holds.
Plumb Bob keeps the part that works and replaces the guesswork. The phone knows exactly where straight down is. The walk to the hole maps the slope along your whole line, not just at your feet. Then it rolls test putts over that surface at your green speed and shows you the one that drops.
slope × distance ÷ speed
The read
Everything a caddie tells you.
- AIMWhere to start itHow far left or right of the cup, in inches, with an aim spot on the grass.
- BRKHow much it breaksIn cups, the way you'd say it to your playing partner.
- PLYHow long it playsUphill and downhill turned into the distance to hit it: an 11-footer that plays 12.
- MAPThe slope under your puttA top-down map of the fall line, and a confidence rating so you know when to trust it.
Green speed
Stimp it with one roll.
Speed decides how much a putt breaks. Don't know today's Stimp? Roll any ball 8 to 15 feet. Plumb Bob tracks it and measures the green speed from how fast it slows. Roll one back the other way to cancel out slope.
measured
Rounds
Get a putting score.
Start on any hole, read your first putt, log how it went. Every putt is scored against a PGA Tour putter from the same distance, so you know exactly how many strokes you gained or lost on the greens.
a tour putter
Stats
See where you lose strokes.
Your make percentage by distance, against tour. Left breakers against right, uphill against downhill. And the one thing to work on next time you're on the practice green.
- 66%Inside 6 ftThe putts that make or break a round.
- 30%Downhill, 3–15 ft"Putt to the plays-like distance, not the real one."
Pricing
Try it on a real green.
Three full reads are free. No account, no card. If it helps you hole more putts, go Pro.
Free
- 3 full reads with the AR line
- Aim, break and plays-like distance
- Slope map and confidence
Plumb Bob Pro
or $9.99 a month
- Unlimited reads and rounds
- Green-speed calibration with one roll
- Putting score, scorecards and round recaps
- Stats by distance and slope, and what to work on
Prices in US dollars; your App Store may show local pricing. The free week is for new subscribers. Payment is charged to your Apple ID and renews automatically unless cancelled at least 24 hours before the end of the period. Manage or cancel in Settings › Apple ID › Subscriptions.
FAQ
Questions, read.
How does a golf green reading app work?
Plumb Bob uses your iPhone's augmented reality tracking to map the green as you walk from your ball to the cup. It measures the slope along and around the line, then simulates putts over that surface at your green speed to find the line that holes out. The line, the aim point and the break are drawn on the grass through the camera.
What is plumb bobbing in golf?
A green-reading technique: stand behind the ball, hang the putter shaft vertically in front of your dominant eye, line its lower end up with the ball and look at where the upper end falls relative to the hole. If the cup appears to one side, the putt tends to break toward that side.
Plumb Bob gives you a truly vertical line from the phone's sensors and measures the slope itself, so the read doesn't depend on a perfectly hung shaft or a level stance.
Do I need an iPhone with LiDAR?
No. Plumb Bob works on any iPhone that runs iOS 17. iPhone Pro models with LiDAR measure the green in depth and give the most precise reads. Other iPhones use camera feature points, which gives rougher reads; scan slowly in good light for the best results.
Can I use it in a tournament?
No. Under Rule 4.3 of the Rules of Golf, using a device to measure or interpret the slope of a green during a competition round is a breach. Plumb Bob is built for practice, lessons and friendly rounds.
How do I measure green speed without a Stimpmeter?
Roll any ball 8 to 15 feet on the green. Plumb Bob tracks it with the camera and works out the Stimp from how quickly it slows down. Roll one back the other way to cancel out slope. Or pick Slow, Medium, Fast or Tour.
What is the putting score?
Strokes gained putting. Each putt is compared with how many putts a PGA Tour player takes on average from the same distance. A positive score means you putted better than tour average; a negative score shows how many strokes you lost on the greens.
How much does it cost?
Three reads are free. Plumb Bob Pro is $9.99 a month or $59.99 a year and starts with a free week for new subscribers. Cancel any time in your Apple ID settings.
Does it need signal on the course?
No. Reads are computed entirely on your iPhone. Only buying or checking a subscription, and finding nearby courses when you start a round, use the network. Nothing about your putts leaves your phone. See the privacy policy.
Read every putt.
Plumb Bob: Golf Green Reader. AR putting line, break and speed for iPhone.