Lost Time Calculator

Track downtime, delays, slow cycles, and reject-related time losses. See where engineering capacity disappears each shift. Export results for audits, planning, and daily improvement teams.

Enter Production and Delay Inputs

Example Data Table

Use this sample to test the calculator and compare shift losses.

Shift Hours Breaks Planned DT Unplanned DT Changeover Delays Minor Stops Ideal Cycle Total Units Defects
8 30 min 20 min 35 min 25 min 15 min 12 min 18 sec 1200 45
10 45 min 30 min 42 min 35 min 20 min 14 min 22 sec 1400 60
12 60 min 45 min 55 min 40 min 18 min 16 min 20 sec 1800 72

Formula Used

Scheduled Time = Shift Hours × 60
Planned Production Time = Scheduled Time − Breaks − Planned Downtime
Run Time = Planned Production Time − Unplanned Downtime − Changeover − Delays
Net Operating Time = Ideal Cycle Time × Total Units ÷ 60
Quality Loss = Ideal Cycle Time × Defective Units ÷ 60
Speed Loss = Run Time − Net Operating Time − Minor Stops
Total Lost Time = Breaks + Planned Downtime + Unplanned Downtime + Changeover + Delays + Minor Stops + Speed Loss + Quality Loss

This engineering model separates losses into availability, performance, and quality categories. It helps teams trace where productive minutes disappear during each shift.

How to Use This Calculator

  1. Enter total shift hours for the production window.
  2. Add break time and planned downtime already expected.
  3. Enter unplanned downtime, changeovers, and delay minutes.
  4. Add minor stop time and ideal cycle time per unit.
  5. Enter total units produced and defective units.
  6. Include operator count and hourly labor rate for cost impact.
  7. Press Calculate Lost Time to show results above the form.
  8. Use CSV or PDF export buttons to save findings.

Why This Calculator Helps Engineering Teams

A lost time study is useful in manufacturing, maintenance, process engineering, plant operations, and line balancing. This calculator highlights downtime, slow cycles, and scrap-related time in one view. It turns raw shift data into measurable operational loss categories for faster corrective action.

Frequently Asked Questions

1. What does lost time mean in engineering?

Lost time is the portion of scheduled work time that does not create planned output. It includes breakdowns, waiting, setup, slow running, and quality-related rework or scrap.

2. Why separate planned and unplanned downtime?

Planned downtime includes expected stoppages like maintenance or meetings. Unplanned downtime shows unexpected failures. Separating them helps engineers improve reliability without confusing scheduled work with true disruption.

3. How is speed loss different from downtime?

Downtime means the process stops. Speed loss happens while running slower than the ideal cycle. Both reduce output, but each needs different engineering actions.

4. Can this calculator support lean improvement projects?

Yes. It helps teams quantify waiting, stoppages, slow cycles, and defects. That data supports kaizen events, bottleneck studies, and continuous improvement planning.

5. Is labor cost loss an estimate or an exact value?

It is an estimate. The calculation multiplies lost hours by operator count and hourly labor rate. It does not include overhead, energy, or material costs.

6. Can I use this for maintenance shutdown reviews?

Yes. Enter planned and unplanned stoppages separately, then compare results across shifts or assets. This helps maintenance teams prioritize recurring causes.

7. What is the largest loss driver field for?

It identifies the single biggest time-loss category in the current calculation. That quick signal helps managers focus improvement effort where it may produce the fastest gain.