# Calculate projected area of polygons with field calculator in ArcMap 10

I've got a polygon featurelayer in arcmap.

The coordinate system of the featurelayer's featureclass is web mercator.

The dataframe of the map uses an equal-area projected coordinate system.

I've got a field on the featureclass called Acreage.

I'd like to calculate Acreage based on the polygon's re-projected area (into that of the dataframe's projection). I don't want to create a new featureclass to do this.

Is there a python script that would let me do this in the ArcMap 10 Field Calculator?

Update: Is there an easy way to do this in ArcMap 10?

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It is not an answer rather it is a question.how do i calculate area in ARCMAP 9.3 Thanks. – user22312 Sep 25 '13 at 7:49
This is not an answer. Ideally this should be a comment on a question or an answer, but I see that you have less reputation, and that is currently preventing you from leaving a comment. I would suggest that you post a new question, detailing how your question is different from this question, and why the answers on this question do not help you out. Also do search a little more searching on our site, to confirm that no existing question solves your issue. – Devdatta Tengshe Sep 25 '13 at 8:22
If you have a new question, please ask it by clicking the Ask Question button. Include a link to this question if it helps provide context. – SS_Rebelious Sep 25 '13 at 9:44
This does not really answer the question. If you have a different question, you can ask it by clicking Ask Question. You can also add a bounty to draw more attention to this question once you have enough reputation. – Sunil Sep 25 '13 at 10:51

Kirk If you are doing this within Arcmap and you have an open table, have you ruled out using the Calculate Geometry option after right-clicking on the field. If your dataframe is already set in the projection that you want you should be able to use its coordinate system without the prior projection issue.

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Ahh, perfect! Glad to see Calculate Geometry actually calculates a number. Thanks! – Kirk Kuykendall Apr 15 '11 at 17:49

There is a way to simple calculate the geometry using Python.

import arcpy arcpy.CalculateField_management('INPUT_SHAPEFILE.shp','ACRES_FIELD','!shape.area@acres!', 'PYTHON')

This will calculate based on the projection information of the dataset.

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XTools Pro, an extension for ArcGIS has a function which will calculate geometry based on any projection you choose regardless of the projection of your data frame.

It's free to download, and there are some features which expire after the trial. But this feature (as well as many others) remain free after the trial period.

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