all total goes to 100%

now you take carbon percent and divide it with 12 and take hydrogen percent divide it 1.008 similarly for nitrogen percent divide it with 14

. now take least value and divide the value you got in earlier part

it will give you an empirical value Cx Hy Nz. incase oxygen is also present  some of carbon hydrogen and nitrogen%-100 is equal to oxygen present

It can be obtained with Chemdraw Ultra 7.0 software. Please draw your structure  or write down the molecular formula on Chemdraw Ultra 7.0 and the highlight it and click on "View" and then click on to "show analysis window". Adjust 2, 3 or 4 decimals as required, in the table. it will show exact  Mass, Mol. wt, m/e and elemental analysis (calculated value).

Assume that 100 g of the compound is available (a+b+c+x=100g):

C ⇒ a g

H ⇒ b g

N ⇒c g

S ⇒ x g [from 100 minus (a+b+c)]

Determine moles:

C ⇒ a g / 12 g mol-1 = a1

H ⇒ b g/ 1   g mol-1 = b1

N ⇒c g/ 14 g mol-1 = c1

S ⇒ x g /32 g mol-1 = x1 (assumed smallest)

Divide by smallest to seek lowest ratio:

C ⇒ a1 / x1 = d

H ⇒b1 / x1 = e

N ⇒c1 / x1 = f

S ⇒x1 / x1 = 1

CdHeNfS

Kindly avail the software's like Chem-draw, Chem-sketch, etc. will provide you accurate numerical value for the respective formula you write/ enter.

Mr. Sergio Reina's explaination is very nice.

Please calculate the molecular formula of your compound followed by calculation of mol weight. If suppose C= 24.09 Divide this no by total mol wt of molecule multiplied by 100 n you will get percentage of C.

YOU CAN USE CHN CALCULATOR AVAILABLE ON INTERNET AS WELL

By using ChemDraw via draw the structure, click on (View), and click on (show analysis window).

or by calculating the molecular weight of the compound then

% atom= (atomic weight *No of atom in strcture) * 100 / molecular weight of the compound

You dan eadily do it from chem draw draw molecular structure first n proceed.