with Texel Density Checker you can:

Calculate Texel Density for mesh for different texture size (includes non-squared textures and custom size)

Rescale UV for getting of target Texel Density

Copy Texel Density from one object to others

Select faces for same Density/UV Space

Visualize Texel Density/UV/Islands with Checker material and vertex color

Texel Density Checker simple for use. You need select your mesh and texture size and just click button.