Area Calculation Problem

[Kikoria]

I had trouble calculating the areas using Zone Tool. Sometimes even with the Fill Tool when I divide the particular shape into several sections, the total area and summed area are different.

Please, see the photo:

in this example the flat's total area is 39.91. When I divide it into room areas and then sum up the parts they sum up to 39.92 and it makes the calculation very risky. I make automatic area calculations but always fear this type of difference and then I have to check everything one by one, so the meaning of automatic area calculation becomes useless in my case.

Could someone please help?

[mthd]

Hi @Kikoria, it’s all ok to check everything by hand as you have done and make the needed adjustments. 0.01 m2 is not going to phase the local authority in calculating the FSR but it can certainly add up when doing quantity take offs and estimating. That’s why you have to make allowances for computer and human errors. Be glad that you checked it by hand never trust a computer estimate unless you have sufficient data on where the discrepancies are occurring. Unfortunately these things can only be controlled by user practical experience. After doing project after project you start to see where you need to be extra careful. When it comes to money it is good to exercise due caution. Let your project manager know and let them take the responsibility. Here is my type of disclaimer “Never trust a computer or your own brain let someone else who is experienced and has more authority look over your work to look for discrepancies” let them accept the liabilities. That’s just my opinion there are many here who know much more than I do so let them guide you.

[Barry Kelly]

It is just a rounding error as you only show 2 decimal places.

I have no idea what the actual areas are, but try this.

If the actual sizes are ...

11.176 will round to 11.18

16.757 will round to 16.76

4.087 will round to 4.09

7.892 will round to 7.89

Total of 3 decimal places

39.912 will round to 39.91

But when rounded to 2 decimal places and you add them together you get 39.92

So by adding rounded figures, you can get a slight inaccuracy.

Barry.

[Kikoria]

Thanks for your reply. Sorry, unfortunately I couldn't get the explanation. The main problem is, with the zones I got 39.91:

These drawings are used to agree on the project and obtain a construction permit.

And the second, detailed square footage is prepared for the sale of apartments, where the sum of the square footage of the areas taken separately must match 39.91, but here it's 39.92 and that creates problems in law:

Could you please explain in more detail how I can make these dimensions match each other? thanks!

[Barry Kelly]

You are showing the areas to 2 decimal places.

That may not be exact areas.

See my example where I used the same figures with 3 decimal places.

The area total is actually 31.912 which when viewed with 2 decimal places will be 31.91

The total area of the large zone before you break it up is not adding all the small areas together, it is just one large area and only gets rounded up or down once.

When you break it into smaller areas, each one of those is getting rounded up or down individually.

More of those must be rounding up, giving you a slightly higher total when you add them together.

You can not control the rounding.

All you cn do is change your units to show more decimal places for better accuracy.

Barry,