Key takeaways
  • Schedule adherence measures whether you made what you planned, in the order and quantity planned, not just whether you made enough.
  • Volume attainment can be 100% while adherence is 60%, because substitutions and resequencing cancel out in the total.
  • Persistently low adherence usually means the schedule was never achievable, not that the floor ignored it.
The score that gets confused with it
Volume attainment

Making the planned total by substituting easier products keeps volume at 100% and destroys adherence. The customers waiting for the products that were displaced experience the difference immediately.

How to measure it

For each scheduled item in the period, take the lesser of planned and actual quantity, sum those across all items, and divide by total planned. Capping at planned is what stops overproduction of one item from covering a shortfall in another, which is exactly the behaviour the measure exists to detect.

Choosing the period

  • Daily adherence is demanding and reveals sequencing problems.
  • Weekly adherence is more forgiving and is a reasonable starting point.
  • Whichever you choose, do not average a low daily figure into a good weekly one and report only the weekly.
  • Measure at the level the schedule is issued at, since measuring more coarsely than you plan makes the score meaningless.

What a low score means

  • The schedule was not achievable: capacity, materials or changeover time were not accounted for.
  • Priorities changed after the schedule was issued, often informally.
  • Breakdowns and quality problems consumed planned time.
  • The floor is optimising locally, for instance grouping similar products to avoid changeovers, which is rational behaviour and a signal about changeover cost.

The most common cause

An unachievable schedule. If planning does not account for real changeover times, real availability and real yield, adherence cannot be met and the schedule stops being treated as a commitment. Once that happens, adherence falls further because nobody believes the plan, which is a self-reinforcing loop that is difficult to exit without visibly fixing the planning inputs first.

Using it well

Pair adherence with the reason for each deviation. The reasons accumulate into a clear account of why plans fail here, and that list is usually more actionable than the percentage. Improving adherence generally means improving the inputs to planning, not exhorting the floor to follow the plan.