Use this calculator to correct your timeslips to a standard correction.
This calculator is based on the SAE J1349 relative horsepower calculation.
Standard conditions are: Air temp 77 °F, 29.235 Inches - Hg pressure, and 0% relative humidity.
The density of air changes which in turn affects the HP generated by an internal
combustion engine. SAE came up with a formula to correct HP numbers based on the air density. Use this calculator to
correct your timeslips. After correcting your timeslips to standard conditions you can more accurately compare the results
The inputs to this calculator are: Air temperature, Dew point, Altitude, Altimeter Pressure (or Altimeter Setting), ET, and Trap Speed.
Air temperature - The ambient air temperature in °F.
Dew Point- The temperature to which the air must be cooled for water vapor to condense and form fog or clouds.
Altitude- Height expressed as the distance above a reference point, which is normally sea level or ground level.
air temperature which is the ambient air temperature, in °F.
Altimeter Pressure (or Altimeter Setting) - That pressure value to which an aircraft altimeter scale is set so that it will
indicate the altitude above mean sea-level of an aircraft on the ground at the location for which the value was determined.
ET - Elapsed Time for your 1/4 mile run, in seconds, from your timeslip.
Trap Speed - The mph for your 1/4 mile run from your timeslip.
How do I get this information? (step by step guide)
- Step 1: Get a timeslip.
- Step 2: Get the weather information. Airports are usually the best source for this information.
National weather service monitors and records the information your looking for.
Use the link and select your state. This will return a page with a few options, choose "Most recently observed weather conditions" drop
down box and select the closest location to the dragstrip.
- Step 3: If you do not know the closest location try using MapQuest. Enter
city and state for a map. Then choose get driving directions to this location. Select places of interest in the
pull down and choose airports. Enter the same city and state as the dragstrip. This will return a list of airports
near the dragstrip. Compare this list to the National Weather Service list to choose
the closest airport.
- Step 4: Go back to the national weather service page and select the closest airport found in step 3 above
and hit go.
- Step 5: The information returned is what you enter into the calculator. Find the closest time to your timeslip
(date and time usually printed on the timeslip). Enter temperature, dew point. Enter the pressure number into the calculator's
- Step 6: Get the track elevation from the dragstrip (they should know it).
- Step 7: Press Calculate and your timeslip will be corrected to standard conditions.