Product Structure Tree Calculator
Example Data Table
| Item | Parent | Qty/Parent | Scrap % | Yield % | Stock | Lead Time |
|---|---|---|---|---|---|---|
| Finished Desk | 1 | 0 | 100 | 0 | 1 | |
| Frame Assembly | Finished Desk | 1 | 1 | 99 | 4 | 3 |
| Metal Tube | Frame Assembly | 4 | 3 | 97 | 20 | 6 |
| Screw Pack | Finished Desk | 1 | 0 | 100 | 14 | 1 |
| Screws | Screw Pack | 12 | 1 | 99 | 200 | 1 |
Formula Used
Gross requirement = parent planned quantity × quantity per parent.
Scrap factor = 1 ÷ (1 - scrap percent ÷ 100).
Yield factor = 100 ÷ yield percent.
Adjusted requirement = gross requirement × scrap factor × yield factor.
Net requirement = maximum of zero, adjusted requirement - stock on hand.
Extended cost = net requirement × unit cost.
Cumulative lead time = parent cumulative lead time + item lead time.
Child items use the parent net requirement. This reduces lower level demand when stock covers a parent assembly.
How to Use This Calculator
Enter the planned build quantity. Add one row for the finished product. Leave its parent field empty.
Add each component under its exact parent name. Then enter quantity per parent, unit cost, scrap, yield, stock, and lead time.
Press Submit to view the exploded tree above the form. Use Download CSV for spreadsheet work. Use Download PDF for a shareable report.
Product Structure Tree Planning
About Product Structure Tree Planning
A product structure tree shows every part inside a finished item. It is also called a bill of materials tree. The top node is the final product. Lower nodes are assemblies, subassemblies, and purchased parts. This calculator expands that tree into usable numbers.
Why This Calculation Matters
A small quantity error can grow fast through many levels. Four screws inside one bracket become forty screws for ten units. Scrap, yield, and stock change the final purchase need. The tool handles those changes in one place. It helps planners see true demand before ordering material.
What The Calculator Measures
The calculator follows parent and child links. It multiplies each child quantity by its parent demand. Then it applies scrap and yield factors. It subtracts available stock to show net requirement. Unit cost is multiplied by net requirement. Lead time is added along each path. The longest path shows a simple critical build path.
Useful Planning Ideas
Use clear item names. Keep each parent name exactly the same everywhere. Enter the final product with a blank parent. Enter its direct children below it. Then add deeper levels for subassemblies. Use percentages carefully. A scrap value of five means five percent extra loss. A yield value of ninety eight means only ninety eight percent passes.
Advanced Uses
The same tree can support buying, costing, and scheduling. You can compare two designs by changing quantities or scrap. You can test stock effects before a production run. You can also estimate what part drives cost. High cost parts with high scrap deserve review. Long lead parts may need earlier ordering.
Best Practice
Review the example table first. Replace the sample rows with your own data. Start with a small tree. Check the results. Then add more levels. Export the CSV for spreadsheets. Download the PDF for sharing. This gives a repeatable planning record for teams, shops, and students. Update stock and lead time often. These values change with suppliers. Keep old exports for comparison. They show how design changes affect total need, total cost, and schedule risk. When data is tidy, the tree becomes easier to audit. Every row explains one relationship. That makes troubleshooting faster during production planning reviews today.
FAQs
What is a product structure tree?
It is a hierarchy of a finished item and its parts. It shows assemblies, subassemblies, and raw items. Each child is linked to the parent that uses it.
What does quantity per parent mean?
It means how many units of a child item are needed for one unit of its parent. For example, four legs may be needed for one table frame.
How is scrap included?
Scrap increases the required quantity. The calculator divides demand by the usable portion. A five percent scrap rate adds extra material for expected loss.
How is yield different from scrap?
Yield shows the percent that passes or works correctly. Scrap shows expected loss. Both can increase the adjusted requirement, so enter realistic values.
Why does stock reduce child demand?
If stock covers a parent assembly, fewer new parent units are needed. Its lower level children are then reduced because they are not required for stocked assemblies.
Can I use decimals?
Yes. Decimals are useful for liquids, wire, fabric, weight, labor, and bulk material. Set decimal places to control how the results display.
What does critical lead time mean?
It is the longest cumulative lead time found through a branch. It gives a simple view of the slowest material or assembly path.
Can I export the results?
Yes. Use Download CSV for spreadsheet analysis. Use Download PDF after submitting the form to save a readable report for sharing.