Stack a few parts together and their tolerances add up — but how you add them changes everything, and how much precision each part really needs.
Tolerance Stack-UpLive
worst-case vs statistical
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When parts stack in an assembly, their tolerances accumulate. Worst-case analysis simply adds them — safe but pessimistic, since all parts rarely hit their extremes together. Statistical (root-sum-square) analysis adds them in quadrature, giving a much tighter, more realistic range. Choosing between them decides how much precision — and cost — each part really needs.
Reading this result: Across 5 parts, RSS (±0.22 mm) is 55% tighter than the worst-case ±0.50 mm — enough headroom to relax individual part tolerances and cut cost.
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How it works
Worst-case tolerance analysis simply sums all part tolerances, guaranteeing fit but assuming every part hits its extreme at once — rare in practice. Statistical root-sum-square analysis adds tolerances in quadrature for a much tighter, realistic range. Choosing between them balances assembly reliability against the cost of tight manufacturing tolerances.
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Is this tolerance stack-up calculator tool really free?▾
Yes. Tolerance Stack-Up runs entirely in your browser using your device's own compute, so local use is free forever. You only pay Compute Tokens if you scale a job to the cloud.
Do I need to install anything?▾
No. Everything runs client-side in a modern browser — no downloads, no license, no account required to start.
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How accurate are the results?▾
The solver uses established numerical methods, but results are for research and educational purposes and should be validated against experiment or professional review before you rely on them.