Completion percentage

What it measures

The share of pass attempts that were caught. It is the oldest passing stat that still gets quoted, and it does say something: a quarterback completing 70 percent of anything is running a functional operation. What it does not say is how difficult the throws were. Depth of target dominates completion percentage; screens complete at 80 percent and 20 yard outs do not, no matter who is throwing.

How it is computed here

We ship the ingredients rather than a pre-baked ratio: completions is the count of complete passes, attempts counts completions, incompletions (including spikes), and interceptions while excluding sacks and two-point tries, matching official passing attempts. Divide them in the builder or the explorer and you have the classic number, at the season, week, or situation-bucket grain.

How fast it stabilizes

Reasonably fast as passing stats go. Completion percentage settles within a season for a full-time starter, because nearly every attempt contributes cleanly. What does not settle is what it means: the number stabilizes around a passer's style (depth of target) as much as around skill.

How it gets misused

• Reading it as accuracy. It is accuracy times throw difficulty. CPOE exists precisely to strip the difficulty out, and it is the better tool for "who is accurate" questions.
• Comparing passers with very different depths of target. A 68 percent short-game passer and a 64 percent downfield passer may be equally accurate.
• Quoting it in tiny splits. Red zone completion percentage over a handful of games is a coin-flip sample; check the attempts column before believing any bucket.