Eyewear, Lenses & Vision Products worked example

Lens Grinding Cycle Time at 13% blocking, setup, and handling allowance: a worked example

Suppose blocking, setup, and handling allowance falls to 13%. This page works the full calculation at that level so you can see exactly which result moves and by how much. Estimate required grinding or surfacing hours for a prescription lens batch using lens count, lab throughput, and setup/handling allowance.

The inputs for this scenario

  • Prescription lenses to grind: 240 lenses (held at the documented default)
  • Grinding throughput: 48 lenses / hr (held at the documented default)
  • Blocking, setup, and handling allowance: 13 % (the input this scenario stresses; the baseline uses 18)

Working through the calculation

  • The calculation starts from the formula this tool documents: Base grinding hours = prescription lenses to grind รท grinding throughput.
  • Required lens grinding cycle time works out to 5.65 hr at these inputs, and this is the headline figure for the scenario.
  • Base grinding hours works out to 5 hr at these inputs.
  • Blocking, setup, and handling allowance works out to 13 % at these inputs.
  • Grinding throughput works out to 48 lenses / hr at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where blocking, setup, and handling allowance sits at 18% and the headline result is 5.9 hr, this scenario comes in 4.24% below the baseline at 5.65 hr.
  • It computes the total grinding cycle time for a lens batch by dividing the count by throughput and adding a blocking, setup, and handling allowance. When the numbers land here, the stressed input is the lever to work; the walkthrough above shows exactly how much each output recovers as it climbs back toward the baseline.

Results at a glance

  • Required lens grinding cycle time: 5.65 hr (headline result)
  • Base grinding hours: 5 hr
  • Blocking, setup, and handling allowance: 13 %
  • Grinding throughput: 48 lenses / hr

Run it with your numbers

  • To rerun this with your own numbers, open the live Lens Grinding Cycle Time calculator, set blocking, setup, and handling allowance to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.