How this instrument works
Passer rating is the NFL's official statistic for summarizing a quarterback's passing performance in a single number, built from four separate components: completion percentage, yards per attempt, touchdown percentage, and interception percentage. Each component is converted onto its own scale and then clamped so it can't go below 0 or above 2.375, before all four are averaged and multiplied by 100 to produce the final rating.
The clamping is what gives passer rating its odd, widely quoted ceiling of exactly 158.3 (a perfect game) and its floor of 0.0 (the worst possible game by the formula's own accounting). Because each of the four components caps out at 2.375, and (2.375 + 2.375 + 2.375 + 2.375) / 6 x 100 works out to 158.33..., no combination of stats can push the rating past that number, no matter how efficient the performance was — a quarterback who completes every pass for huge gains and never turns the ball over simply maxes out all four components at once.
The formula was adopted by the NFL in 1973 as a standardized way to compare passers across a season and across eras, replacing a patchwork of earlier ranking systems. It has been criticized for decades for being opaque — the clamps and scaling constants aren't intuitive from the raw stats — and for ignoring sacks and rushing entirely, but it remains the league's official rating and the number printed on broadcast graphics and official box scores.
Each of the four components on its own tells you something specific: the completion-percentage component rewards accuracy, the yards-per-attempt component rewards explosive, down-field production, the touchdown component rewards scoring efficiency, and the interception component (which runs in the opposite direction, starting high and being reduced by interceptions) penalizes turnovers. Seeing all four side by side, as this calculator shows, reveals which part of a passer's game is driving — or dragging down — the final number.
- Enter Completions and Attempts — the pass-completion counts for the game or season you're rating.
- Enter Passing yards, Touchdown passes, and Interceptions for that same span.
- Read Components a, b, c, d — each shows where that part of the formula landed, clamped between 0 and 2.375.
- Read NFL passer rating — the average of the four components, scaled to the league's familiar 0-to-158.3 range.
- If a component reads exactly 0 or 2.375, the clamp has been triggered — that piece of the performance was extreme enough to hit the formula's floor or ceiling.
Worked example — 20-of-30, 250 yards, 2 TD, 1 INT
A quarterback completes 20 of 30 attempts for 250 yards, with 2 touchdowns and 1 interception. Component a = clamp((20/30 - 0.3) x 5, 0, 2.375) = 1.833333. Component b = clamp((250/30 - 3) x 0.25, 0, 2.375) = 1.333333. Component c = clamp((2/30) x 20, 0, 2.375) = 1.333333. Component d = clamp(2.375 - (1/30) x 25, 0, 2.375) = 1.541667.
None of the four components hit their clamps in this game — all sit comfortably inside the 0-to-2.375 range. The final rating is ((1.833333 + 1.333333 + 1.333333 + 1.541667) / 6) x 100 = 100.694, a solid, well-above-average passer rating for a single game.
Questions
Why does passer rating cap out at exactly 158.3?
Each of the four components — a, b, c, and d — is individually clamped so it can never exceed 2.375. If all four hit that ceiling at once, the average is (2.375 x 4) / 6 = 1.58333, and multiplying by 100 gives 158.33, rounded to the widely quoted 158.3. No combination of real stats can push the formula higher, which is why a 'perfect passer rating' game is always reported as exactly 158.3.
Can passer rating go below zero?
No. Each component is clamped with a floor of 0 as well as a ceiling of 2.375, so even a catastrophic game — very low completion percentage, negative yards per attempt, zero touchdowns, and a high interception rate — can only drive each component down to 0, never negative. With all four components at their floor, the rating bottoms out at exactly 0.0, not below it.
What does the interception component actually measure?
Component d runs in the opposite direction from the other three: it starts at the maximum of 2.375 and is reduced as the interception rate (interceptions divided by attempts) climbs, using the formula 2.375 minus (Int/Att x 25), clamped to stay within 0 and 2.375. A quarterback who throws no interceptions keeps this component at its ceiling; a high interception rate can drive it all the way down to zero.
Does passer rating account for sacks or rushing yards?
No — the formula only uses completions, attempts, passing yards, touchdown passes, and interceptions. Sacks, which reduce a team's overall efficiency and are heavily influenced by pass protection and play design, don't appear anywhere in the calculation, and neither does any rushing production by the quarterback. This is one of the formula's most common criticisms, since it can reward a quarterback's passing stats while ignoring costly sacks taken on the same drives.
Is NFL passer rating the same as college or NFL 'total QBR'?
No, they're different metrics. NFL passer rating uses the fixed four-component formula described here, unchanged since 1973 and identical across every game and season. Total QBR is a separate, more modern metric developed later that incorporates additional context like down-and-distance, game situation, and some credit for rushing, and it isn't computed with a simple public formula the way passer rating is.