The three things to look at first when you read a green

Most missed putts come down to the read, not the stroke. Here are the three things to check as soon as you get to the green, together with the physics that explains why they matter.

1. The direction of the steepest slope

Start by working out which way water would run off. The break is largest when the slope runs straight across the ball–cup line, and there is no break at all when it runs straight up or down it.

The sideways acceleration from gravity is simply:

a = g · sin(slope angle)

That is 0.17 m/s² for 1°, and 0.34 m/s² for 2°. The important point is not that "2° breaks twice as much as 1°" — it is that the break grows with the square of the time the ball is rolling. Even at the same 1°, a downhill putt that keeps running will break far more.

2. The green speed

A Stimpmeter reading tells you how many feet a ball rolls when released at a fixed speed. On a faster green the rolling resistance is lower, so the ball keeps rolling for longer over the same distance.

In other words, the faster the green, the bigger the break. A line that is one cup out at 10 feet can easily be two cups or more at 13.

3. The last metre before the hole

The ball breaks most sharply just before it reaches the cup. As the speed drops, the same sideways acceleration bends the path far more:

curvature = sideways acceleration / speed²

Halve the speed and the curvature goes up four times. That is why, when you settle on a line, reading the last metre carefully beats taking in the whole putt vaguely.

Check it for yourself

Enter the distance, slope and Stimpmeter value into the Putt Break Calculator and it will give you the break and the apex (the point of maximum sideways deviation) as numbers. Comparing those against your own read shows you where you tend to over- or under-estimate.