The Measure Of A Fastball Has Changed Over The Years

A fast fastball is a lot faster than it used to be.

On Sept. 24, 2010, Aroldis Chapman threw the fastest recorded pitch in major league history.

His 105.1 mph fastball was the first time the 105 mph barrier had been broken. It wasn’t Chuck Yeager breaking the sound barrier, but it was significant.

But Major League Baseball now registers that pitch as a 105.8 mph fastball. Over the course of the past decade, Chapman’s fastest fastball had gotten faster by nearly a mile per hour. What was a 105 mph fastball can now be said (with rounding) to be the first recorded 106 mph pitch in MLB history.

How can that be? It all comes down to where the pitch is measured.

The moment a baseball leaves a pitcher’s hand, it starts to slow down because of drag. According to University of Illinois physicist Dr. Alan Nathan, a pitch that leaves a pitcher’s hand at 100 mph will (at sea level) slow down by 9 to 10% by the time it crosses the plate some 55-58 feet later.

So that 100 mph pitch could be measured at 100 mph (at the pitcher’s hand), 99 mph (at 50 feet from home plate), 94 mph (midway on its journey) or 91 mph (as it crosses home plate)—the rate of decrease varies based on atmospheric pressure, so a pitch at the altitude of Denver’s Coors Field slows less than a pitch at Tropicana Field in St. Petersburg, Fla.

The Pitch/FX system that MLB used in 2010 measured pitches at roughly 50 feet from home plate, which is where the 105.1 mph of Chapman’s fastball was measured. The current MLB Statcast system measures velocity as the pitch leaves the pitcher’s hand. MLB has gone back and recalibrated Pitch/FX pitches to convert them to their velocity at pitch release. That’s why Chapman’s fastest fastball found an extra .7 mph.

For decades, comparing pitch velocities has often been an apples-and-oranges discussion. The first radar guns that began appearing at ballparks in the late 1970s and early 1980s measured pitches much closer to the plate. The Speedgun, developed by Decatur Technologies (a long-time maker of police radar guns) measured closer to the plate than the JUGS gun. For scouts, the Speedgun was known as the “slow gun” while the JUGS gun registered faster readings and was the “fast gun.”

Then Stalker came out with its Pro Sports radar gun in the early 1990s. It measured velocity closer to the pitcher’s release point than the JUGS gun, so the JUGS flipped to being the slow gun.

A 90 mph pitch on a Speedgun could register at 92 on a JUGS gun and 93-94 mph on a Stalker. The tech continued to improve. A 94 mph pitch on the Stalker Pro registered as 95 on the Stalker Pro II.

So when you read of 85-90 mph fastballs from the early 1980s, realize that they would be registering much faster with current measurement tech. An 85 mph fastball (if registered by a Speedgun at the plate) would be roughly 93 mph if measured by Statcast out of the pitcher’s hand.

And that makes the 100 mph pitches Nolan Ryan threw in 1974 (as measured by Rockwell laser/radar instruments relatively close to the plate) even more remarkable today.

Now that Statcast has been measuring pitches since 2007, and has adjusted all of those pitches to the same scale, we now have a consistent scale to measure pitches, which leads to the question: are pitchers throwing harder, or are we just measuring the pitches closer to the hand?

Every year, MLB pitchers are throwing harder than they were before. In 2007, the average four-seam fastball measured out of the hand at 91.9 mph. In 2023, the average four-seam fastball measured out of the hand at 94.2 mph. Over the past 16 years, there has never been a season where the average four-seam fastball velocity has dipped from the previous year.