SMV and CM cost calculator
Two steps, one page: turn a stopwatch reading into an SMV, then turn that SMV into a CM price per garment using your real line cost and your real efficiency.
1. Time study → SMV
SMV = observed time × (rating ÷ 100) + allowance.
Average of your stopwatch readings for the operation. 45 seconds = 0.75 min.
100 = standard pace. Below 100 for a slower operator, above for a faster one.
Relaxation, personal needs and machine delay. 15–20% is typical in sewing.
SMV / SAM
0.863minutes
Basic time
0.750min
Allowance added
0.112min
SMV and SAM are the same number; factories differ only in which label they print on the bulletin.
2. SMV → CM cost per garment
CM = SMV × cost per minute, where cost per minute is line cost ÷ earned minutes.
Everything absorbed into CM: wages, benefits, supervision, allocated overhead.
Cosmetic only - no exchange rates are applied.
CM per garment
5.03BDT
0.863 min × 5.8275 BDT/min
Cost per minute
5.8275BDT/min
Daily output
9,183pcs/day
At the efficiency entered above.
Available minutes / month
374,400min
Earned minutes / month
205,920min
Dividing by available minutes instead of earned would price this garment at 2.76 BDT - 2.26 BDT short on every piece. That gap is exactly the efficiency you are not running at, and it is the most common error in a costing sheet.
How this is calculated
Step 1 - basic time. A stopwatch records how long this operator took, which is not the same as how long the job takes. Rating corrects for pace: basic time = observed time × (rating ÷ 100). An operator rated 80 was working slower than standard, so the basic time is lower than what you timed; one rated 115 was working faster, so it is higher.
Step 2 - SMV. A stopwatch reading excludes everything that is not the job itself, so an allowance is added: SMV = basic time × (1 + allowance ÷ 100).
Step 3 - cost per minute. This is where costing sheets go wrong. Available minutes are operators × days × hours × 60. Earned minutes are available minutes × efficiency. Cost per minute is line cost ÷ earned minutes - not ÷ available minutes, because the line does not produce during the minutes it loses.
Step 4 - CM. CM per garment = SMV × cost per minute. Daily output falls out of the same figures: (operators × hours × 60 × efficiency) ÷ SMV, which is the number to check a promised delivery date against before you accept it.
Questions
- Is SMV the same thing as SAM?
- Yes. Standard Minute Value and Standard Allowed Minutes are the same figure calculated the same way; factories differ only in which label they print on the operation bulletin.
- What allowance percentage should I use?
- 15 to 20 percent is typical for sewing, covering relaxation, personal needs and unavoidable machine delay. Heavier or hotter operations justify more. The right number for your floor comes from your own allowance study, not from a rule of thumb.
- Why divide the line cost by earned minutes instead of available minutes?
- Because you only recover cost on the minutes the line actually produces. Dividing by available minutes prices the garment as though the line ran at 100 percent efficiency, and under-recovers by exactly the efficiency gap. At 55 percent efficiency that understates CM by almost half.
- What belongs in the monthly line cost?
- Everything your costing policy absorbs into CM: operator and helper wages, benefits, supervision, and the share of factory overhead allocated to that line. Fabric and trims are not CM - they are material cost, quoted separately.
- Why is my calculated CM higher than the price the buyer pays?
- Usually because the efficiency assumed in the quotation was higher than the line actually runs, or because overhead was allocated across more lines than are really working. Both show up here as a cost-per-minute that is higher than the one used at quotation.
- Does a higher rating mean a better operator?
- Rating describes pace against a 100 standard during the study, not skill or quality. Rating is the most subjective part of a time study, which is why two officers timing the same operation can produce different SMVs - rate against a benchmark your work-study team has agreed on.
Sources & verification
The rating-and-allowance method is standard industrial work study, as taught in the ILO's Introduction to Work Study and used by every garment work-study department. The arithmetic is not in dispute; the inputs are.
The output is only as good as three judgements this calculator cannot make for you: the rating you assigned, the allowance your factory has agreed, and what your costing policy absorbs into CM. Change any of those and the CM changes with it.