# How to calculate area in a binary image?

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Asmalina Mohamed Saat
on 17 Sep 2020

Commented: Image Analyst
on 13 Oct 2020

I have two questions to ask:

1) How to calculate area at the white region in binary image?

2) How to convert the answer of area unit that get from matlab into cm^2 or mm^2 (SI UNIT)?

here I attach the original image and binary image (this image is marine growth on the fiberglass plate)

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### Accepted Answer

Deepak Meena
on 22 Sep 2020

Hi Asmalina,

1) To find the area in pixel size we just need to find the number of white pixel which would be

area = bwarea(bw);%bw is your binary threshold image

The unit would be pixel

2) To find the area in real world units , you need to find out how big one pixel is in appropraite units, if you working with DICOM image refer to this answer.

Another way is we can find the percentage of white area so if you have the plate area , you can find out the actual white area then.

to find out the percentage area:

percentageWhite = nnz(bw) / numel(bw);

##### 5 Comments

Image Analyst
on 25 Sep 2020

### More Answers (1)

Image Analyst
on 22 Sep 2020

See my attached spatial calibration demo.

##### 12 Comments

Image Analyst
on 13 Oct 2020

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