Sectional density calculation

[Benhmt]

I have a question regarding the calculation for the sectional density of any bullet. I am aware of the formula, which, as I read it goes as such. Bullet weight divided by 7000 (to convert grains to pound), that sum is then divided by the bullets caliber (in inches), then squared. I do this and get a result that is close (allways higher) to what I see in loading manuals but I know that mathematically I should get exactly the same number I see in my manuals. Her is an example of what I am doing. Take the 175 grain .308 bullet for an example. I am dividing 175 by 7000 to get the sum of .025, then I divide .025 by .3082 to get .0811, then I square .0811 to get .284
My loading manual shows a result of .264
I have tried this formula in many different calibers and weights and always end up about 20 hundredths high. I know I am overlooking some small detail, can someone shed some light on this for me.
Thanks

 

[Catfur]

Square the caliber before dividing by it.

 

[Benhmt]

Thanks for the response, I tried what you suggested. The grain weight in pounds is .025, and the caliber of .3082 squared is .5551 What I did this time is to divide .025 by .5551 for the sum of .0450, then I squared that and ended up with the sum of .212 The number in this example that I should be getting is .264 Something is still not right. Any further thoughts?

 

[Catfur]

.5551 is the square root of .308, not the square. .308 squared is .095.

 

[Benhmt]

Thank you, I sorted that out on my own too. Long time since high school math class for me. In my defense, the manual that I got all of this from shows the formula like this: 175/7000/.3082 equals .264
That equation gets you to the sum of .0811
Then I googled it and found this equation:
175/7000/.3082 squared
That equation (as I interpreted it) said to square the sum of 175/7000/.3082
You have resolved my frustration with this and I thank you.
Ben