Give me some simple formula for to calculate min & max size values using scaling
 

sir ,
i am using ANSYS 12
i have a problam in meshing
i am using patch independent tetra mesh.
sir i want some simple formula or procedure for calculate
1.min size
2.max size

using data like geometry size ( X, Y, Z direction length).

Min Size = minimum gap size / 5...10

Max Size = maximum gap size / 10

With that values you have at least 5 to 10 elements in your smallest gap and at least 10 elements in the largest gap. Take this as an first assamption and find values that are reasonable for your project.

I agree with Max E.'s suggestion as a good way to start.

However, it is very model and situation dependent (no one size fits all). Also, you could have a global min size and a smaller local min size...

You will probably need to come up with your own rule-of-thumb based on your own specific needs.