All of that is taken into account, of course. But there's more. Sometimes, the coaches measure progress by watching his feet. Are they turned properly?
Sometimes it's by asking a question: Why did you make that throw? His answer helps reveal any growth.
And, make no mistake, the second year of Howell's development is a big key to Washington's season. He has worked all spring and summer as the Commanders' starting quarterback, ahead of veteran Jacoby Brissett. Though coach Ron Rivera has told reporters a couple of times "don't sleep on Jacoby," the job remains Howell's to lose.
Through two weeks of camp, there have been good days and tough ones; good throws and bad ones. Just as the team anticipated. The Commanders remain impressed with Howell's command of the huddle, his leadership and his work ethic -- all aspects necessary to building a starting quarterback. They also know he's inexperienced -- with one start and 19 pass attempts -- and that it takes time to become a good NFL quarterback.
One rep, Howell can throw a well-placed ball to Terry McLaurin, away from an oncoming safety and beyond the corner's reach. But another time, he can force a pass in traffic that gets deflected or intercepted.
"Sam's still learning everything in this offense, just like the rest of us," Washington tight end Logan Thomas said. "He's made his fair share of mistakes, just like the rest of us."
The next two weeks will tell a lot about Howell's growth -- as well as for the entire offense. The Commanders will open the preseason on Friday at Cleveland and then will conduct a two-day joint practice with Baltimore on Aug. 15-16.
"When you start narrowing the scope of what he's doing, that's where you've got to see the growth," Rivera said. "The preseason games will be really good for him."
But it's not just about Howell. Washington must learn new coordinator Eric Bieniemy's offense while practicing daily against a veteran defense in the fourth year of a system, one that finished third in yards per game and seventh in points last season. The Commanders also have new starters at four offensive line spots.
Rivera has said often about the offense, "It will take time."
Bieniemy has installed a high volume of plays; coaches say they'll obviously narrow their playlist for games -- which, they said, will help Howell. For now, they're running through a lot to see what the offense retains, to see what works.
Rivera also will point out that he's facing a complex defense every day -- one adept at disguising coverages. And, he said, Howell is limited with making checks or audibles. On July 29, Howell and the offense had a particularly bad day. They improved during the week, culminating with a better showing Wednesday before having an up-and-down day Friday.
"He's had a very good week compared to what happened on Saturday," Rivera said. "And the thing I've got to understand, too, is look at the massive amounts of information that he has to process every meeting."
In the spring, Howell said he would call plays into his phone and play it back, listening to his cadence and the conviction of his calls. He wanted to hear how it would sound to others in the huddle.
Before some practices in camp, when the three quarterbacks were working on taking snaps from center, quarterbacks coach Tavita Pritchard would call out a play -- and Howell had to repeat it out loud for the others.
"At this point, I have total command of the offense," Howell said earlier in camp. "I feel like in the spring I was kind of still learning because that was kind of the first time I saw all the information and now I've had that spring and now I'm really comfortable."
As Howell learns the offense, the players continue to learn about him. They like how he stays even-keeled. The receivers love how he'll continue to throw downfield, more than the other quarterbacks in camp. Friday, for example, he tried to connect with receiver Dyami Brown deep down the middle with a defender in front and behind him.
"He just has a really good feel of throwing the ball down the field," McLaurin said. "He's going to give guys a chance to make the play down the field and he throws a really nice deep ball.
"It's really cool to see a young guy who's not afraid to continue to give his guys catches or guys opportunities down the field."
Other times, Howell just wants to see if he can stick in a throw. Earlier this week, for example, Howell opted for a secondary target, with the primary receiver open. Howell made it more difficult. Rivera asked him a simple question: Why?
Howell told Rivera, "I had that coach, but I wanted to see if I can make that throw."
That, Rivera said, is what training camp also is for: seeing what throws he can make or can't make.
"He's growing," Rivera said. "I like how he's doing and how he's communicating with us as well."
The coaches measure Howell’s development in part by where the ball hits the receiver. If he's not hitting them in stride, Rivera said, it's often because he's late getting to his read or his feet aren't in sync with his eyes.
Sometimes Howell will see the play right, but, Rivera said, he needs to process it faster.
"That's one of the things that's been really cool is to watch him when you see him recognize it and process it," Rivera said. "Part of it though is his timing has to get a little bit better when he does see it and get to it."
"It's [about] process," Pritchard said. "What were you thinking here? What did you see? How were you processing this? We can't be results based because if we just look at complete, incomplete, interception, it's not right. Was it a tipped pass? Was it the rush? So staying process-oriented is really important."
There are aspects in which Howell has been ultra-consistent, like how he handles negative plays.
"You really don't even see him get flustered even when he's had a few, maybe rough patches during practice. He doesn't hang his head," McLaurin said. "He's not yelling, cussing things like that. He said he's pretty even keel, which is really unique for a young guy like that."
"He used to be that quiet guy," Thomas said. "He's really taken this, this leadership role of the starting quarterback and ran with it and you know, he demands us to be, to be really, really good."
If Howell emerges as they hope, then perhaps Washington will have solved its longtime quarterback quest. Rivera has started eight different quarterbacks (including Howell) in his first three seasons. Heinicke has the most starts (24) since Kirk Cousins left after the 2017 season.
In the past five years, Washington has the NFL's worst total QBR (37.8); not so coincidentally, the Commanders have a .384 winning percentage in that span.
"It's been great so far and I'm excited to work with him," McLaurin said, "and hopefully he's going to be our guy for the future."