# How to Calculate Man to Machine Ratio for a Double Shift Plant? Normally, the man to machine ratio (MMR) is calculated considering a single shift. Though sometimes factories work overtime for 2-4 hours in a day, I have never seen or heard that factories derive Man to Machine ratio differently for OT hours. This question is an eye-opener for engineers for thinking it differently when we calculate man to machine ratio for a factory.

In machine productivity calculation, we consider working hours per shift. Factories used to define their productivity as units produced per 8 hours shift or units produced in 10 hours shift. Factories convert overtime hours into manpower, where 8 hours equal to one manpower.

Normally, garment factories don't work for double shifts. Though it is common that textile mills and processing houses work for 24 hours (3 shifts) a day. In my 15 years of working in the garment industry, I know only one factory in Romania that works double shifts in a day. The double shift means the same set of sewing machines and equipment are utilized for two different shifts in a day.

I had never calculated man to machine ratio for double shift plant. As I have received this question, I am sharing my views on how man to machine ration should be calculated for a double shift plant. When machines are utilized for two shifts, machines should be counted twice for man to machine calculation. Otherwise, if we count machines only once and count total manpower including two shifts' attendance, man to machine ratio will be near to double of the actual MMR ratio, which would be an incorrect presentation of the MMR of a factory. I hope you will agree with me on this.

To make the MMR realistic, I would suggest using the following formula for calculating man to machine ratio where a factory works two shifts in a day.

Man to machine ratio = (Total manpower of shift one + total manpower of shift 2)/ (Total machine utilized in first shift + total machines utilized in the second shift).

Also Read: Man to machine ratio calculation method

It is not necessary that you need to agree with my views.

In case your views are different, please feel free to share it with us. If you are calculating man to machine ratio differently or if you are considering Overtime hours in calculating man to machine ratio please share it with us.  You can post your comment in the following comment box or send your answer by email to me.