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
Share of scheduled hours that are productive.
Your results
A simplified single operation model. Real routings sum several operations, overlap them, and use calendar rules. Validate against your ERP scheduling.
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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ERP fixes and how-tos
- NetSuite MRP Not Generating Planned Orders: Causes and FixesWhy NetSuite supply planning creates no planned orders: item planning fields, time fences, lead time, lot sizing, demand source, and how to firm and release.
- Infor M3 MRP not creating planned orders: what to checkChecklist for Infor M3 MRP that creates no planned orders for an item: planning method, item-warehouse setup, time fences, supply and the MRP run itself.
- Infor LN Enterprise Planning Not Generating Planned OrdersWhy Infor LN Enterprise Planning produces no planned orders for an item with demand, and a step by step check of planning data, horizons and order policies.
Guides
- When SyteLine MRP Is Not Generating Planned OrdersSyteLine MRP not generating planned orders? Work through item planning flags, horizon and cutoff dates, order policy, existing supply, and failed planning runs.
- Infor M3 Supply Chain Planning: Settings That Actually MatterInfor M3 supply chain planning deep dive: planning methods, safety stock, planned orders, distribution orders, and MRP tuning that reduces expedites.
- Infor LN Freeze/Unfreeze Planning: Frozen Zones and Time Fences ExplainedHow Infor LN freeze and unfreeze planning works: frozen zones, time fences, firm planned orders, and Enterprise Planning settings that stop MRP nervousness.