# Convert values from square meter to square kilometer in ArcMap

I am using ArcMap 10.3.1 on a Windows x64 system.

I use the Universal Soil Loss Equation (USLE) to calculate the average annual rate of erosion on a field slope based on rainfall pattern, soil type, topography, vegetation system and management practices.

A= R*K*LS*C*P

A represents the average annual soil loss in tonnes per square kilometer per year (t km−2 yr−1); R stands for rainfall erosivity factor; K is the soil erodibility factor; LS is the slope length-gradient factor C is dimensionless vegetation cover factor; P refers to the soil conservation practice.

In my case, all the data are 30m spatial resolution, and I calculate each parameter in ArcMap. So the spatial resolution of my soil erosion raster map is 30m, which means the unit is in tonnes per 900m2 per year.

I’d like to convert unit from ‘tonnes per 900m2 per year’ to ‘tonnes per square kilometer per year’. I know that the Resample tool, block statistics, Focal statistics tool, and Zonal statistics tool in ArcMap are useful for changing the resolution of a raster to a coarser cell size, but it will mass values (e.g.Figure 1). I want to change the units used for area value, but without loss value. But I do not know how to convert this in ArcMap.

Figure 1

• Just so I understand, you don't want to change your area or mass value, but simply change the units used for the area value? If so, you just need to divide you're m2 value by 1000000. Or are you looking to for how much mass is in 1 km2? – danielm Feb 2 '17 at 19:03
• What is your question? Are you wanting to know how to convert, or what tools to actually convert the numbers, or whether your methodology is correct? – Midavalo Feb 2 '17 at 19:29
• @danielm, thanks for your help. I have edited my question. After divide the m2 value by 1000000, the new value ranges from 0 to 0.00355203. My case study is a serious erosion areas and compare with other published papers and scientific reports, I think this value is too small. Any other suggestion? – user121 Feb 3 '17 at 0:03
• @Midavalo, thanks, I have edited my question, and my question is that I want to know how to convert the units without mass values in ArcMap. – user121 Feb 3 '17 at 0:18
• @user121 to convert m2 to km2 you must divide by 1 million – Midavalo Feb 3 '17 at 0:23