How this calculation works
An equal-time average of speeds uses the arithmetic mean. Equal distances make the reciprocals add as travel times.
THE FORMULA
H = 3/(1/a + 1/b + 1/c)A worked example
For equal distances at speeds 30, 60, and 90, the average speed is about 49.09.
Good to know
All three values must use the same units.
Reference: OpenStax Algebra and Trigonometry (opens in a new tab) ↗
Read the result
Average positive rates when the quantities covered at each rate are equal.
The primary result is labeled “Harmonic mean”. Keep the input definitions in view when comparing this result with another method.
Try a related calculation
All three values must use the same units.
For a related exercise, try the quadratic equation solver.
A few questions, answered
How can I check the default inputs by hand?
For equal distances at speeds 30, 60, and 90, the average speed is about 49.09.
Which rule does this calculator apply?
H = 3/(1/a + 1/b + 1/c)