Calculating composite wire gauge

Can anyone tell me how to calculate the composite wire gauge for a pair of wires of different gauges? Or better still, for any number N of wires of N different gauges? I know how it works for two wires of the SAME gauge. For example, two 22 gauge wires combine to yield a 19 gauge composite: you subtract 3 from the common gauge 22. But how, for example, do a 22 gauge wire and a 19 gauge wire form a composite gauge? I can pin it down this much: two 22's yield 19, as in my first example, and two 19's yield 16, by subtracting 3, so a 22 and a 19 must yield a value between 16 and 19. That's as far as I can take it. Anyone know an equation?
Try the following link - - it may help you. Regards, Richard,
22AWG has a Standard Metric Size diameter of 0.63mm. 19AWG is 0.90mm. 0.63 + 0.90 = 1.53mm which is 14.5AWG.
Sorry, my last posting is incorrect. I should have used Cross-sectional area. 22AWG = 642.4 circular mils. 19AWG = 1,288. 642.4 + 1,288 = 1930.4. 17AWG is 2,048 so it's almost 17AWG.
Thanks Vantageaudio and Citation! What a great forum, to be able to get accurate information on an abstruse topic like this, and within a few hours. I now know what I need to know. I guess the cross sections for the series of gauges were set in such a way that doubling any of them matched the one three steps down, so that combining two gauge X's yields gauge X-3, wherever X happens to be in the series. I'm grateful for your help.