The NFL's passer rating formula looks intimidating — four sub-components, a scaling constant, a 158.3 ceiling — but each piece is answering a specific, simple question about a quarterback's box score. Here's what the formula is actually doing and why it's shaped the way it is.
The four things it measures
Passer rating combines four rate stats, each converted onto the same 0–2.375 scale:
a = ((Comp ÷ Att) − 0.3) × 5
b = ((Yards ÷ Att) − 3) × 0.25
c = (TD ÷ Att) × 20
d = 2.375 − ((Int ÷ Att) × 25)
Rating = ((a + b + c + d) ÷ 6) × 100
- a rewards completion rate above a 30% baseline
- b rewards yards per attempt above a 3-yard baseline
- c rewards touchdown rate
- d penalizes interception rate, starting from a ceiling and subtracting
Each of those four numbers is capped at 0 on the low end and 2.375 on the high end before they're averaged — that clamp is the reason a wild single-play outlier (like one 99-yard touchdown skewing yards-per-attempt) can't blow the rating outside its normal range.
Why the weird baselines (0.3, 3 yards)?
The 30% completion-rate baseline and 3-yard-per-attempt baseline aren't arbitrary — they were set, per the NFL's own history of the formula, to roughly reflect replacement-level (below-average) quarterback performance at the time the formula was adopted in 1973. A quarterback performing right at those baselines contributes 0 to that component; better performance pushes it positive, worse performance pushes it negative (down to the 0 floor).
Why it caps at 158.3
Each of the four components maxes out at 2.375. Sum four maxed components (2.375 × 4 = 9.5), divide by 6, multiply by 100, and you get exactly 158.3 — a "perfect" game under the formula's own math, not an arbitrary round number.
What it deliberately leaves out
Passer rating only uses five official box-score inputs: completions, attempts, yards, touchdowns, and interceptions. It does not account for:
- Sacks — a quarterback who's sacked eight times but completes every pass he does throw still scores identically to one who's never sacked
- Rushing production — a mobile quarterback's rushing touchdowns and yards are invisible to this formula entirely
- Situational context — a garbage-time completion counts the same as a fourth-quarter, two-minute-drill conversion
This is exactly why ESPN built Total QBR as an alternative — a separate, proprietary metric that weighs sacks, rushing, fumbles, and game situation. QBR isn't publicly reproducible from a simple formula the way passer rating is, which is also why we don't calculate it here: every tool on this site is grounded in a documented, closed-form formula, and QBR's exact weighting isn't published.
College and other leagues
The formula above is the NFL's own. NCAA football uses a different "passing efficiency" rating with its own formula and scale — don't assume a college passer-efficiency number and an NFL passer rating are directly comparable, even though both are sometimes casually called "passer rating."