The Secret to Calculating Takt Time in Your Head, Fast

People are always amazed when I do takt time calculations lickety-split in my head. Here’s my secret: it’s the result of a lot of practice with doing math in the head, and memorizing a few nifty net available time numbers. This formula:
Takt time = Net available time per shift / customer demand per shift
is simple division.
The denominator of customer demand per shift is a given based on a number you will derive either from a monthly or weekly average, or true orders that must ship each day. Unless you commit the sin of overproduction, or foolishly choose not to deliver what your customer will buy, the customer demand number is set for you, by your customer (or by planning).
The numerator of net available time per shift is the fun number, and the first part of the secret to calculating takt time in your head, fast. Memorize these useful numbers:
3,600: the number of seconds in one hour
27,000: the seconds in a 7.5 hour shift (8.5 hours 1 hour of breaks)
28,800: the seconds in a 8.0 hour shift (9 hours minus 1 hour of breaks)
30,600: the seconds in a 8.5 hour shift (10 hours minus 1.5 hour of breaks)
37,800: the seconds in a 10.5 hour shift (12 hours minus 1.5 hour of breaks)
These are the net available times you will most frequently encounter when doing takt time calculation. Simply divide the appropriate one of these by the customer demand number, and voila, you have takt time.
The second part of the secret to calculating takt time in your head, fast, is years of being drilled in multiplication and division tables in Japanese elementary schools, decades before they introduced “education with breathing room”. Practice may not make perfect, but it makes proficient.

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