Backyard putting green speed: measuring stimp the USGA way and picking a target

01What does a stimp number actually measure?

How far a ball rolls. The Stimpmeter is a 36-inch aluminum bar with a V-shaped groove. A ball sits in a notch about 30 inches from the tapered end, and the notch releases it when the bar is raised to about 20 degrees, so every ball leaves the bar at the same velocity (USGA Stimpmeter Instruction Booklet). The average distance in feet is the green’s speed. A green that “runs a 10” rolls that ball 10 feet.

The USGA made the device available to courses in 1978 and modified it in 2012 for undulating greens. Its purpose is steadiness more than speed: the USGA says the Stimpmeter’s main job is keeping green speeds “consistent and appropriate” (USGA Stimpmeter 101). On a backyard green that means a number to come back to after a winter or a sand top-up.

02What speed should a backyard green run?

Start with the greens you actually play. The USGA says Stimpmeter readings on American golf courses “generally range from 7 feet to 12 feet.” Ask your course what its greens run on an ordinary week, not a tournament week, and treat that as a starting point rather than a target to copy exactly, because the USGA also says the Stimpmeter “is not intended for course comparisons.”

The published numbers side by side:

The 10-foot caution is about keeping grass alive, which a synthetic green doesn’t have to do. The rest of the USGA’s advice holds at home: “Faster is not necessarily better, nor should it be the goal,” in part because greens that are too fast slow play. A practice green much quicker than your course trains you for putts you won’t see on the weekend.

A manufacturer’s rating is the range its surface can be set within. How much sand goes in, and how it is brushed and rolled, decide where in that range a particular green lands.

Speed and slope are chosen together. The USGA calls it an unfair challenge when a green is so fast, or a hole cut in such a spot, that a ball can’t be stopped near the hole from any point on the green. The faster the green, the gentler the slope a cup can sit on; how much break works at which speed is in how much slope a backyard putting green can have.

03How do you measure green speed the USGA way?

You need a Stimpmeter, three golf balls, three markers and a 12- or 15-foot tape. The USGA sells its Stimpmeter for $120, with a handling fee added to shipping (USGA shop). The steps, from the USGA’s booklet:

1. Find a level stretch 10 to 12 feet long. Readings taken up or down a slope, or over mounds, mislead.
2. Roll three balls from one spot along the stretch. Raise the bar slowly until each ball releases, and hold it steady until the ball reaches the green.
3. Check the spread. The three should stop within 8 inches of each other; if not, roll the series again. Mark their average stopping point.
4. Roll three back from that mark toward the start, along the same line.
5. Average the two distances. That is the green’s speed. If the two directions differ by more than 18 inches, the stretch wasn’t level enough; pick another.

Most backyard greens are built with break everywhere, so a long level stretch is hard to find. Stimpmeters made after 2012 carry a second, half-length notch for that:

A USGA agronomist adds details that make readings repeatable (USGA Green Section Record):

• Use the same spot every time. Mark the start and a second point at your target distance, so the rolls tell you at a glance whether the green is on target.
• Line up the ball’s seam with the Stimpmeter’s. A ball that rattles down the groove can roll short.
• Raise the bar slowly and pause when the ball releases. Raising it too fast or too high inflates the number.
• Wait after grooming. For grass, the advice is at least 30 minutes after mowing or rolling, because earlier readings run high. The same wait after brushing or rolling a synthetic green keeps your readings comparable.

The USGA also has a video of the whole test.

04What makes a synthetic green read faster or slower?

On grass, mowing and watering move the number. On a synthetic green, these do:

• The surface. Each putting turf has a speed range built in. The two ratings in the table above, from one maker’s two nylon surfaces, run from 9 to 12.5.
• The infill. Synthetic Grass Warehouse, a turf distributor, says a synthetic green’s stimp speed “can be adjusted by varying the type and amount of infill used,” with denser infill rolling faster than looser infill (Synthetic Grass Warehouse). Too much or too little leaves an uneven surface that affects the roll (Synthetic Grass Warehouse).
• Rolling. The same company’s installer column recommends pressure rolling after the infill goes in, which presses the fibers down to the infill height and evens out Stimpmeter speeds (Ask JW).
• Water. The USGA says moist turf is slower than dry turf, and even a small amount of surface moisture slows the roll. Synthetic Grass Warehouse says moisture that can’t drain off a synthetic green changes its speed as well.
• Wind. The USGA sets a green’s baseline speed on a calm day and treats windy-day readings as a separate condition.

05When should you re-measure a green in Northern Colorado?

Take the baseline once, in the USGA’s conditions: a dry, smooth surface on a calm day. After that, measure whenever something changes, and write each reading down with the date and the weather. The USGA’s booklet lists windy days and wet surfaces among the conditions to record separately, and tells you to “Keep thorough records.” Here that means:

• Pick a still morning. The Colorado Climate Center describes the plains as having “moderate to high wind movement.” A reading taken in a gusty afternoon belongs in the windy-day column, not the baseline.
• Let the green dry after a storm. The Climate Center says hot summer days on the plains “are often relieved by afternoon thundershowers,” and that Colorado’s generally low humidity “favors rapid evaporation.” That suggests a soaked green dries quickly here, but nobody has measured how quickly, so check the surface is dry before you roll.
• File winter numbers as winter numbers. The nearest NOAA station, Fort Collins, averages 150 nights a year at or below 32°F (1991–2020 normals). A reading on a frosty or frozen green is an unusual condition in the USGA’s sense: log it, but don’t change the sand to chase it.
• Re-measure after the spring brush-out. The same station averages 51.4 inches of snow a year, and spring is when a green gets brushed up and sand is topped off where it has thinned. The amount of infill sets the speed, so October’s number may not be May’s. Spread sand only on dry turf: Synthetic Grass Warehouse’s column says infill placed into turf holding any moisture affects the roll and the Stimpmeter speed.

06What should you ask an installer about speed?

• What speed will the green be set to, and can I choose it? A good answer is a number or a narrow range, tied to the surface’s published rating.
• Which surface is it, and what does its maker rate it at? Ask for the spec sheet with the stimp range printed on it.
• How is the speed set? For a sand-filled green: how much infill, and how it is brushed and rolled. For a surface without sand: what, if anything, can change its speed later.
• Will you stimp it at handover? A good answer names the test stretch, rolls both directions, and writes the number down for you, so you have a baseline to check after the first winter.
• What will move it later? Ask how a sand top-up or brushing changes the number, so you know what to adjust and when to call.

How greens are built, from base to cups and fringe, is on the putting greens page, and the rest of the putting green guides cover size, surfaces and care.