How to calculate duct area in meters for rectangle duct ?

2 X ( Width + Height) X length

For example0.5 m width and0.3 m height and10 m length

2 X (0.5 +0.3) X10

2 X (0.8) X10

2 X8 =16 sq.m

Hope this will work

2(W+H)*L

FOR EXAMPLE,

L=10M,W=3M,H=1M

ANS:

=2(3+1)*10

= 2(4)*10

=8*10

=80 SQ.MT

ANS = 240 SQ.MT

Duct quantity can be estimated in sq. mts. or kgs.

For duct estimation in sq. mts., one needs to first find the perimeter of the duct section, i.e.2(W+D) & multiply it by the straight length. It is an usual practice to tabulate it in excel sheets using formulae to estimate the overall quantity. It involve basic knowledge of geometry & being familiar with MS excel to use formulae. Further the duct sections can be categorized as per the gauge to be used depending upon the largest dimension (reference from SMACNA & DW144)

For estimation in kgs. multiply the size in sq. mts. with the density specific to the gauge to be used. There are many spreadsheets available form various source, even internet. But for beginners, especially the ones who are curios to know working behind the worksheet, I recommend to generate your own excel sheet. It will surely consume lot of time in the beginning, but it builds up the basic knowledge that last forever.

Before you get in to the estimation you have to consider two things in the drawing sheet

1) units of height and width of a duct. Mostly it would be in millimeters.

2) scale of the drawing sheet.

To calculate the rectangular duct area, we need height, width and length.  Standard Autocad drawings shows the width and height of duct at various regions where as length should be taken out using a hand scale by measuring the duct at each positions. 

Then to get area in meter square, use the equation

2(W+H)*L; where W is Width, H is height and L is Length of duct

ALL UNITS SHOULD BE IN METERS

Scaling of drawings are mostly done in1: . That is1 cm on your scale is1 meter in reality, which can be directly substituted in the above equation. 

Example for a duct of * in mm with sheet scale1: and hand scale measures5 cm.

Area would be2(2.1+2.1)*5 = square meter =. sqft.

Surface Area of rectangular duct(Sq. metre)=2*(width+height)*length

All dimension should be in meter,

if you want to get in sq. ft then 

Area(sq. ft)= 10.762* Sq. metre

Measure one side of the duct from top to bottom, then measure the bottom of the duct from left to right, if the duct is square or rectangular. Use a measuring tape that measures in inches. Use the calculator to add these two measurements together and multiply by two. This tells you the length of the perimeter of the duct.

Measure the length of the duct--in inches--and multiply that measurement by the length of the perimeter of the duct. This will tell you how many square inches are in the duct area. Divide this result by 144, the number of square inches in a square foot. This will tell you how many square feet are in the duct area.

Measure the distance across the duct, in inches, then multiply by 3.14159 if the duct is circular to find its circumference, in inches. Then, measure the length of the duct--in inches--and multiply by the circumference. This is the number of square inches in the duct area. Divide by 144 to determine how many square feet are in the duct area.

Converting an area to square feet would seem simple, unless the area is spread over a form with height, width and depth. Then, you have to convert the outside of that form, its perimeter and length into a workable flat surface and convert the area of that flat surface to square feet.

A = (2*(W+H))*L

THE AREA OF RECTANGULAR DUCT ,WE CAN CALCULATE BY THIS  GENERAL FORMULA AREA=2(W+D)*LENTH ,OR WE CAN ALSO FIND OUT REVIT SOFTWARE.

Area = 2(Width + Height) * Length this for rectangular duct