Coast Down Test Calculator

Analyze vehicle drag from coast-down (deceleration) test data per SAE J2263.

Vehicle Weight (Test Weight)

lbs

Frontal Area

sq ft

Test Data Point 1 (High Speed)

Start Speed

MPH

End Speed

MPH

Time

seconds

Test Data Point 2 (Low Speed)

Start Speed

MPH

End Speed

MPH

Time

seconds

Coast Down Test Tips

Perform tests on flat, level road
Test in both directions to cancel wind/grade
Minimize wind conditions (<5 MPH ideal)
Use consistent tire pressures
Run multiple tests and average results
Ensure transmission in neutral
Record ambient temperature and pressure