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Planned Order Offset and Start Date Calculator

MRP back schedules a made-in-house order from the due date using a lead time offset. If that offset is too short orders start late; too long, you build early and hold stock. This calculator builds the number from its parts.

Your numbers

units
hours
hours
85 %

Share of scheduled hours that are productive.

8 hours
days
days
days

Your results

Offset rounded up (days)
6
Use whole days when your ERP stores lead time that way.
Share of time spent processing
49.5%
Total run hours
18
Scheduled process hours
23.5294
Setup plus run, divided by efficiency.
Process days
2.9412
Total offset
5.9412
Days between order start and due date.

A simplified single operation model. Real routings sum several operations, overlap them, and use calendar rules. Validate against your ERP scheduling.

Save results:

Total offset vs order quantity

Sweeps Order quantity from 10 to 500, holding your other inputs fixed.

Check routing lead times against history

Optional: ask about comparing planned offsets with actual job durations.

Optional. The tool and every export work without this. No spam.

How to use it

Enter the order quantity, setup hours and run hours per unit from your routing. Set efficiency, the hours the work centre really runs per day, and the non-touch time: queue before the operation and move or wait time after it. Add any safety lead time you apply. The result is the offset in days and the share of that time spent actually working, which is often much smaller than people expect.

The formula

Process hours equal setup plus quantity times run time, divided by efficiency. Process days are process hours divided by work hours per day. Total offset is queue plus move plus process days plus safety. The chart sweeps quantity so you can see how a larger lot raises run time while setup stays fixed. Queue and move typically dominate small orders, which is why shortening them often beats speeding up the machine.

  • Process hours = (setup + qty x run) / efficiency
  • Offset = queue + move + process days + safety
  • Round up if your ERP stores whole days

Mistakes and ERP notes

Do not double count: if your ERP routing already adds queue and move per operation, enter them once here. Do not use theoretical run times with no efficiency. For multi-operation routings, sum the operations or use the ERP's scheduling run; SAP computes lead time scheduling in routing and production order scheduling, and Epicor and SyteLine schedule from the job routing. Review fixed lead times on items that are made at different lot sizes.

Frequently Asked Questions

Is offset the same as lead time?

In practice yes for planning: it is the time between the start and the due date of an order. Some systems split it into in-house production time and processing time, so check your ERP's definition.

Why include efficiency?

Standard times assume ideal performance. If a cell typically delivers 85 percent of scheduled hours, dividing by that factor gives a more realistic duration.

Should I add safety lead time?

Only to cover real, measured variability. Hidden padding in every field adds up and inflates the lead time, which pushes MRP to release earlier and carry more work in process.

Does this replace finite scheduling?

No. It is an infinite capacity estimate. Use your scheduler for load aware dates.

Netray can compare the offsets in your ERP with actual job start and finish history, read-only.

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