Horsepower In The Air

NHRA Elevation Correction Factors

Use this chart to convert your e.t. and mph to sea-level performance by multiplying either e.t. or mph performance at a given altitude by the indicated factor. These are NHRA's correction factors for normally aspirated Stock and Super Stock race cars, which equate the best for a typical normally aspirated street car. These factors are used to "correct" back to sea level as a way of establishing class indexes.

As an example of how to use this chart, if your car runs 12.00/114 mph at a 3,000-foot-altitude track, use the correction factors (e.t. x 0.9640 and mph x 1.0381) to generate altitude-corrected numbers equaling 11.568 at 118.34 mph. These are roughly 311/42 percent corrections for that altitude. Keep in mind that these factors correct only for track altitude, they do not address the existing weather conditions. This is a way to roughly compare a normally aspirated car's performance at Denver's Bandimere Speedway (at a wheezy 5,800 feet) to your buddy's Englishtown, New Jersey, rocketlike e.t.'s running at a track that is virtually at sea level. It's also worth noting that NHRA uses a less aggressive correction factor for the quicker Competition Eliminator cars. Plus, most supercharged and turbocharged cars (AA/Altered Turbo for example) use half of the Comp correction factor. Alcohol dragster and Funny Cars are not factored.

Get Converted

These conversions come courtesy of the HP Books Auto Math Handbook by John Lawlor. Some data also came from Metals Progress Databook.