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Advanced Technical Reference

Industrial Engineering Formulas

A practical formula reference for SMV, efficiency, capacity, productivity, line balance, and WIP.

Industrial Engineering Formulas

01

Time Study Formulas

Industrial engineering converts observed work into a repeatable standard minute value.

Normal time = observed cycle time × performance rating
Standard time = normal time × (1 + allowance %)
SMV = sum of operation standard minutes
Average cycle time = total observed time ÷ valid cycles
Performance rating 100% represents defined normal pace
Exclude abnormal cycles only with a documented reason

02

Efficiency and Productivity

Earned-minute formulas connect good output with labour time and approved work content.

Earned minutes = good output × garment SMV
Available minutes = direct operators × working minutes
Efficiency % = earned minutes ÷ available minutes × 100
Labour productivity = good output ÷ labour hours
DHU = defects found ÷ units inspected × 100
First-pass yield % = right-first-time units ÷ total units × 100

03

Capacity and Planning

Capacity calculations convert manpower and SMV into achievable output at a planned efficiency.

Hourly capacity = manpower × 60 × efficiency ÷ SMV
Daily target = available minutes × efficiency ÷ SMV
Required manpower = target × SMV ÷ minutes ÷ efficiency
Takt time = available production time ÷ demand
Pitch = takt time × pack quantity
Plan only good output; include a realistic quality loss assumption separately

04

Line Balancing and WIP

Balance metrics reveal station loading, bottlenecks, and flow instability.

Balance efficiency = total work content ÷ stations × bottleneck cycle time × 100
Balance loss % = 100 − balance efficiency
Theoretical minimum stations = total work content ÷ takt time
WIP days = work in process ÷ average daily output
Throughput time includes processing, transport, queue, and delay
Bottleneck capacity sets the line ceiling unless work is redistributed

05

Worked-Control Guidance

Formulas are useful only when units, manpower scope, break treatment, and good-output definitions are consistent.

Use decimal efficiency in calculations: 80% = 0.80
Keep seconds and minutes consistent before division
Separate direct from indirect manpower
Remove planned breaks from available minutes consistently
Recalculate after method, layout, machine, or SMV changes
Compare calculated capacity with sustained hourly performance

Apply buyer-specific manuals where requirements are stricter.