How can I measure my staff loyalty for the company?

The best way is to have a quarterly or yearly satisfaction survey.  Make sure that each questions has a comment box in the event that the employees would like to elaborate.  Also, at the last part of the survey, there should be another box, where the employees can suggest the next questions to be included in the next survey, or add feedback about the survey.

Very important to assess employees happiness or satisfaction level for better productivity and improvement. More satisfied employees are more loyal and productive and with low chances of going for alternate. Best way to measure loyalty is through question and suggestion boxes in questionnaire attached with appraisal or through group and individual meetings to see how much they are align with company .

Do the job as it is required.

Be honest 

Listen, understand and follow the instructions.

Always focus on the duty

Move the work without wasting time 

The attendance record is always best

Presentation of the results will prove his intense work

Going for prayer and God feared

Keep interaction with his team and higher management

Always telling truth and don't cheating people

Present in his work place with performing his assignments

Don't create panic but resolve problems and bring maximum company benefits

Keep the record of his payments, expenses, bills and never tell lie what he done.

Assess:

1. Time.

2. Effort.

3. Detication.

4. Acountability.

5. Commitment.

Make sure that each questions has a comment box in the event that the employees would like to elaborate.  Also, at the last part of the survey, there should be another box,The Contractor complaints from the site staff and their intervention. It means that the staff is loyal

In addition to said above, by feedbacks of your clients. 

Thank you.

By seeing his intentions

If the staff is punctual at site. The quality of work is better u see at the site visite. The client is happy with the site activities. The Contractor complaints from the site staff and their intervention. It means that the staff is loyal

In a online loyalty survey, employees can be invited to answer how meaningful they think their work is, how often they feel some sort of stress in the workplace, etc. Their personal opinions are valuable as information from other viewpoints. The consideration of a company, its activities, the opportunities it offers is most reliably accomplished by considering different points of view, and an employee loyalty survey is indispensable in that respect.

I am not sure if you can measure their loyalty, but you certainly can check it.