Enter your Measured Horsepower, Temperature, Barometric Pressure, Humidity, and Elevation, then choose a Correction Standard (SAE, STD, or DIN) to calculate your Corrected Horsepower, Correction Factor, Dry Air Pressure, and Vapor Pressure.
Corrected Horsepower
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Correction Factor
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Dry Air Pressure
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Vapor Pressure
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SAE J1349 uses standard conditions of 77°F, 29.234 inHg, and 0% relative humidity, while SAE J607 uses 60°F, 29.92 inHg, and 0% relative humidity. J1349 is the more commonly used modern standard for automotive dyno testing.
Air density varies with temperature, pressure, and humidity, affecting engine power output. Correction factors standardize your results to allow fair comparisons between runs taken in different weather conditions or at different locations.
Always use station pressure (actual pressure at your location), not the weather-corrected barometric pressure. Weather services often report pressure corrected to sea level, which is not what you need for dyno calculations.
Higher humidity reduces air density because water vapor is lighter than dry air. This means less oxygen is available for combustion, resulting in lower power output. The correction factor accounts for this effect.
At higher elevations, atmospheric pressure decreases, reducing air density and available oxygen. This results in lower power output. The correction factor compensates for altitude effects on engine performance.
SAE correction factors provide standardized calculations based on atmospheric physics and are widely accepted in the automotive industry. However, individual engines may respond differently to atmospheric conditions based on their design and tuning.
This calculator applies to naturally aspirated engines. Turbocharged and supercharged engines have different responses to atmospheric conditions because forced induction partially compensates for air density changes.