Tolerance Stack-Up Calculator
Upload your drawing or describe your dimension chain. Get worst-case and RSS stack-up results, violation flags, and specific corrective tolerance recommendations — in seconds.
Run Your Stack-Up FreeNo credit card required · Free plan includes 10 analyses/day
Capabilities
Full tolerance analysis in one tool
Worst-case & RSS analysis
Run both worst-case (WC) and root sum square (RSS) tolerance stack-ups. See the gap range, assembly yield estimate, and which dimension chain is the controlling variable.
Upload CAD or paste dimensions
Upload STEP, DXF, or PDF drawings and ForgePilot extracts the dimension chains. Or paste your dimensions and tolerances directly into the prompt.
Automatic violation detection
ForgePilot flags any dimension chain where the stack-up closes out of spec under worst-case conditions — with the exact violating dimension highlighted.
Corrective tolerance recommendations
For each violation, get a specific tighter tolerance recommendation with the tradeoff cost — machining class, process change, or design revision.
GD&T-aware analysis
ForgePilot understands geometric tolerances — flatness, perpendicularity, true position — and includes them in the stack-up where specified.
Export analysis report
Export the full stack-up table and narrative as a PDF or Markdown report, ready to attach to a design review or supplier package.
Common stack-up scenarios
Any dimension chain with a critical gap or fit — ForgePilot handles it.
Shaft-hole fit analysis
H7/g6 and similar fits — interference, clearance, and transition check.
Assembly gap analysis
Multi-component stacks where gap closure is safety-critical.
PCB mounting tolerance
Connector, standoff, and board edge dimensional chains.
Weld joint geometry
Weld gap, joint prep angle, and root opening stack-up.
Optical system alignment
Lens centering, focal plane, and mounting tolerance chains.
Medical device assembly
ISO 13485 compliant tolerance analysis for implant and device fits.
Frequently asked questions
What is a tolerance stack-up calculator?
A tolerance stack-up calculator analyzes a chain of dimensions and their tolerances to determine the cumulative variation at a critical gap or interface. It tells you whether your assembly will always close within spec (worst-case) and the statistical yield (RSS). ForgePilot does this from your dimension inputs or CAD files without requiring a spreadsheet.
What is the difference between worst-case and RSS tolerance analysis?
Worst-case (WC) analysis assumes every dimension is at its worst allowable value simultaneously — guarantees 100% yield but often results in very tight tolerances. Root Sum Square (RSS) analysis treats variations statistically and typically gives a more economical tolerance set at a defined yield level (e.g., 99.73% at ±3σ). ForgePilot calculates both.
Can ForgePilot read dimensions from a drawing or CAD file?
Yes. Upload a PDF drawing, DXF, or STEP file and ForgePilot extracts the relevant dimension chains for the analysis. You can also describe or paste dimensions directly into the chat.
Does it support GD&T tolerances?
Yes. ForgePilot understands form, orientation, and position tolerances (flatness, perpendicularity, true position, etc.) and includes them in the stack-up when specified in your drawing or prompt.
Run your tolerance stack-up now
Upload a drawing or describe your dimension chain. Get worst-case and RSS results, violations flagged, and fix recommendations in seconds.
Launch Workspace Free10 free analyses per day · No credit card required