MSTEngineering Intelligence

Compare BOM Revisions and See Exactly What Changed

BOM Compare takes a Before and an After bill of materials, matches parts by part number, and marks each one Added, Removed, Changed or Unchanged — so you see the effect of a revision before you update an assembly or place an order.

01

What it does

  • Matches parts by exact, case-sensitive part number.
  • Compares quantity, description and material for parts in both BOMs.
  • Shows the quantity change (After minus Before) and the fields that changed.
  • Filterable result table, exportable as CSV (bom-comparison.csv).

02

How to compare two BOM revisions

  1. Export each revision from your CAD, PDM or spreadsheet as CSV UTF-8.
  2. Load the Before and After files, paste CSV text, or select "Try sample revisions".
  3. Map columns: Part number and Quantity (required); Item, Description, Material (optional).
  4. Select "Compare BOMs" and filter by status.
  5. Export the comparison and review it against your drawing change record before purchasing or assembly.

03

How parts are classified

  • Added: part number only in the After BOM.
  • Removed: only in the Before BOM.
  • Changed: in both, with a different quantity, description or material.
  • Unchanged: all three match.

04

Input rules

  • UTF-8 CSV or TSV, up to 4 MB per file, or pasted text. Excel workbooks are not read directly — save as CSV UTF-8 first.
  • Each part number must appear once per BOM; the tool names any duplicate.
  • Quantities: plain non-negative numbers, dot decimal, up to six decimal places, no units or thousands separators.

05

Know the limits

It compares flat BOM tables only. It does not compare CAD geometry, rebuild assembly hierarchy or approve part substitutions.

06

Why teams use it

Design engineers catch revision changes without line-by-line spreadsheet checks, and engineering managers get a clear, exportable change list to review before parts are ordered or assemblies updated.

07

FAQ

Is BOM Compare free?

Yes, and it includes sample revisions to try first.

Which formats are accepted?

UTF-8 CSV and TSV up to 4 MB each, or pasted CSV text.

Which fields are compared?

Quantity, description and material, for parts matched by part number. Map Description and Material on both sides to see those changes.

Why does a part show as both removed and added?

Matching is exact and case-sensitive — check for extra spaces, capitalization, or letter O vs. digit 0.

Why was my file refused?

Usually a duplicate or missing part number, a quantity with units or separators, or non-UTF-8 encoding. The message names the row or part.

Does it compare CAD models?

No, flat BOM tables only.

How do I get a BOM out of a drawing first?

Use the free Drawing to BOM tool and export CSV.

MST AI Engineer

Beyond BOM tables

BOM Compare is a free tool from MST. MST AI Engineer takes a P&ID gas-line diagram plus your approved PDM parts and equipment rules and builds a native, editable SOLIDWORKS assembly — starting with semiconductor gas equipment.

Start a team trial