How To Work Out Square Footage.

What you are going to need: 

• A scale ruler. if you don't have one to hand then a 30cm 
• A sharp pencil. or beter a retractable pencil.
• rubber (just in case).
• Floor plain of the shop.

A scale ruler has 8 scales printed on it 

1:1, 1:100, 1:20. 1:200, 1:5, 1:50, 1:1250 and 1:2500.

One of these will be the scale of your shop plan. if not, you can use a regular ruler with the CM scale.

1:1 scale this is real life scale mainly used for jewellery and smaller things rather then floor plains.
1:100 scale 1cm = 1 meter
1:20 scale. 1cm = 200mm (millimetre) 20cm
1:200 scale. 1cm = 2 meters. 200cm
1:5 scale. 2cm = 100mm (millimeters), 10cm
1:50 scale. 2cm = 1meter
1:1250 scale. 1cm = 12.5meters
1:2500 scale. 1cm = 25 meters

(1:125 and 1:2500 scale are used for maps on occasion for the main ground plans for a shopping centre.)

If you are using a scale ruler the measurements are already worked out for you, 

The first thing to do is to break down the floor in to squares and triangles. This will make an odd shape shop floor easier to calculate.

On the image above you can see where I have broken down the floor (the blue lines) in to areas due to the shape of the floor, to help able to work out the floor area.

Next step is to measure each shape and note them on the plan

To find out the area of a square or rectangle multiply A x B
for example: 
A= 3.9cm
B = 4.4cm
3.9x4.4=17.16 sq cm

To find out the area of a triangle multiply A x B and divide by 2.
for example:
A= 3.9cm
B = 4.4cm
3.9x4.4 = 17.16 divide 2 = 8.58sq. cm

Next add the area of each of the shapes together to get the area of the floor.

If your not using a scale ruler then your answer will be in square centimetres.

So if you have a floor measuring 600sq. cm

1:100 scale 600sq. cm = 600sq. meter
1:20 scale. 600sq. cm = 12000mm (millimetre) 120sq. meters
1:200 scale. 600sq. cm = 1200 meters
1:5 scale. 600sq. cm = 3000sq. mm (millimeters) 30sq. meter
1:50 scale. 600sq. cm = 30000sq. meter
1:1250 scale. 600sq. cm = 7500sq. meters
1:2500 scale. 600sq. cm =  15000sq. meters

The math.
Your cm sq footage from your plain = Z 
1:20 scale.  Z x 20 =
1:200 scale. Z x 200
1:5 scale.  Z x 5=
1:50 scale. Z x 50=
1:1250 scale. Z x 125=
1:2500 scale. Z x 25=

Not many companies use feet and inches these days but if is a handy thing to no the Sq foot 

of your  store. 

To convert Sq. meters in to Sq. feet (ft) multiply by 10.76

for example: 

17.2 Sq. M x 10.76 = 185 Sq. ft.