Jobs per square mile is one of measures for urban density. For a neighborhood, if it has a great amount of job opportunities within neighborhood or within adjacent areas where can be approached by walking or biking in a moderate time period, say 15 minutes, then I think it might be a more sustainable than neighborhoods with very limited jobs from the perspective of economy and public health.

The equations can be:

For strict boundary of neighborhood,
Amount of jobs within neighborhood/ amount of adult, healthy residents in neighborhood

Or a neighborhood with a commuting buffer area by walking or biking:
Amount of jobs within neighborhood and buffering area/amount of adult, healthy residents in neighborhood