Calculating an Arc
from Mark Gunter's old website

Mathematics For Woodworkers
Calculating an Arc

Arc Math (Height, Width, and Radius)

  • Enter the two measurements of the arc that you know.
  • Press the title button of the remaining box to compute the third measurement.

  • The Formula:
    The formula to compute arc measurements is:
  • 2hr = h2 + (w/2)2
  • where
  • h = height
  • w = width
  • r = radius

  • Example
    To find the radius of an arc that is .75 inches high and 3.5 inches wide:
  • enter .75 for height
  • enter 3.5 for width
  • press Radius button
  • The answer (2.41667) is computed and displayed

  • Hints
  • If you only know one number you can play with the remaining numbers to work out two that fit.
  • The box titles are submit buttons - don't look for a special "submit" or "compute" button. Simply fill in the known values, then press the button next to the box that represents the value to be computed.

  • Credits
    Thanks to Joel P. Watson for this javascript calculator, Mary Ann Watson - Joel's LOML, proofreading Doug Watson - scripts, testing

    This site is maintained by:
    Good-Lyddon Data Systems

    Copyright © 2004-2007 Joe Lyddon,