Equation Not Producing the correct result

I have been trying to figure out my mistake on the following equation...

Ft = ((-24.5 * ((0.667 * (wind * 8/5)) + 4.8)) + 2111) * (-4.8 - ((Temp-32) * 5/9)) ^ -1.668

On a previous post (http://www.excelforum.com/excel-gene...750)...someone suggested

=SUM(-24.5*((0.667*B9*8/5)+4.8),2111)*SUM(-4.8,-(B8-32)*5/9)^-1.668

If I plug in the following...

wind = 5
Temp = -10

I am supposed to get the following answer 31

However this equation which looks right to me is giving me an answer of 14.29

I found someone who is calculating this formula using the following in a java script... FBT2 = ((-24.5 * ((0.667 * ((FBTwind * 8) / 5)) + 4.8)) + 2111) * (Math.pow(-4.8 - (((FBTtemp - 32) * 5) / 9),-1.668)) and this one does produce the correct results. They are using this at ... http://weather.stadhaugh.com/Frostbite2.html

They look like they should do the same thing, so not sure why I am getting different results. I have attached a spreadsheet along with a table of various answers to help.

It seems that it is not an Excel issue, it is the equation where the problem is occurring.
Can you manually show us the calculations for how 31 is reached from wind = 5 and temp = -10 so we implement it in excel.

This kind of thing gets frustrating. Debugging strategies I tend to use for something like this:

1) Break the computation up into smaller bites. There are a lot of parentheses in the current formulation, and it is easy to get parentheses out of place. For example, it appears that the original equation is based on temperatures in C and wind speeds in km/hr, so parts of the current formulation are performing the unit conversions. I would tend to pull the unit conversions out and do those separately and make sure that the unit conversions are correct.

2) Research the equation to make sure that it is applicable. Are you certain the values in the table were calculated from the equation, or are the tabulated values the experimental result and the equation is a "best fit" of the tabulated values? Other limitations on the equation? For example, this page (http://schools.cbe.ab.ca/b274/pdfs/Wind%20chill.pdf ) claims that the proposed equation is only valid for wind speeds above 15 kph and times below 15 min. If I restrict your equation to those inputs, it appears to match the tabulated values pretty well, though not exactly. This suggests to me that the tabulated values are not from the equation, but the equation is an empirical fit of the table.

I'm not quite satisfied with this, either, but it might suggest a direction for your research.

I suppose I have been intrigued by the question.

This is more debugging stadhaugh's javascript, but I found this little bit interesting.

If I put -10 F and 5 mph in (units to F), then it calculates 31 minutes.
If I put -23.33333 C and 8.047 kph (units to C), then it calculates 22 minutes.

Like you and thisoldman, I get 14.3 minutes from the equation. I, too, cannot see how one gets 31 (or 22) minutes from the inputs you are using.