Stimpmeter Green-Speed Converter
Enter a Stimpmeter reading to get a plain-language speed category, the green’s effective rolling friction, and how far the same putt rolls up versus down a slope you choose.
Green speed
The downhill and uphill figures are how far the same delivery speed would roll on the slope you entered — the gap between them is why a downhill putt needs a far softer touch than an uphill one of the same length.
Why green speed and slope go together
Green speed is really a measure of friction: a fast green resists the ball less, so the same push sends it further. The Stimpmeter turns that into a number everyone can compare by always launching the ball at the same speed. From that reading you can recover the surface’s effective friction, and once you know the friction you can predict how the ball behaves on a slope — which is where putting is actually won and lost.
The uphill and downhill roll figures make the point visible. On a quick green a modest downhill grade can double the roll, while the uphill version of the same putt dies quickly. Good putters read that instinctively, adjusting pace long before they think about line. Working the numbers here builds the same instinct: feel how a couple of percent of slope reshapes the roll, and the touch starts to make sense.
Frequently Asked Questions
How do I take a reading the USGA way?
Pick a level spot. Rest the tapered end on the green, put a ball in the notch and slowly raise the bar until the ball rolls (about 20 degrees). Roll three balls; they should stop within 8 inches of each other, or repeat the series. Then roll three back along the same line from where they stopped. The speed is the average of the two directions; if the two differ by more than 18 inches the spot is not level enough. On a slope, enter both averages in the optional boxes and the tool applies Brede's correction, 2 x up x down / (up + down), which the plain average overstates.
What is a Stimpmeter reading?
A Stimpmeter is a simple angled rail that releases a ball onto the green at a repeatable speed of about six feet per second. The distance the ball then rolls, measured in feet, is the reading, so a green that rolls the ball 9 feet is 'running at 9'. Higher numbers mean faster greens. The USGA built it to help a course keep its own greens consistent, not to compare one course with another.
What counts as fast or slow?
As a general guide, readings under about 6.5 feet play slow, 6.5 to 8.5 is medium, 8.5 to 10.5 is fast, and above 10.5 is tournament pace. Most well-kept everyday greens sit in the 7 to 9 range; the lightning-fast greens you see at professional events are often 11 or more, which is why the pros treat downhill putts with such care.
How does slope change the roll?
Gravity adds to the ball's momentum going downhill and works against it going uphill, so the same delivery speed rolls much further down a slope than up it. The calculator solves the energy balance for the grade you enter and reports both distances — the gap between them is exactly why a downhill putt needs a far softer touch than an uphill putt of the same length.
Why does it say a putt 'does not stop' on a steep slope?
When a slope is steeper than the green's friction can hold, gravity overcomes friction and a ball nudged downhill keeps accelerating rather than coasting to rest. The tool flags this because it's a real feature of fast, sloped greens — on the quickest surfaces, some downhill positions are effectively impossible to leave the ball near the hole from, which is why pace and position matter so much.
Educational estimate using a simplified rolling-resistance model; real greens vary with grain, moisture, and surface. Use it to build feel, not to grade a green precisely.