NormCalcEngineering tools
Tolerance stacks · statistical analysis

Tolerance Stack Calculator

Analyze linear tolerance stacks using worst case, RSS, and reproducible Monte Carlo simulation. ISO 286 tolerance classes can be resolved by the validated fits core.

Σ1D
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Tolerance stack

Positive dimensions increase and negative dimensions reduce the closing dimension.

DimensionFree name for the stack element, for example housing width, spacer, or bearing seat. Unique names make the resolved-dimension review easier.+/−Sensitivity direction in the closing dimension: plus increases and minus reduces the result. Example: A − B gives a 12 mm closing dimension for A = 20 mm and B = 8 mm.NominalTheoretical basic size without deviation. Tolerance is applied relative to this value; for example 20 mm with −0.1/+0.2 mm.SourceManual uses the entered deviations. ISO 286 resolves the lower and upper deviation of a supported class directly through the validated ISO 286 core.ToleranceFor manual input, enter the lower deviation on the left and upper deviation on the right in millimetres. Example: ±0.1 mm becomes −0.1 and +0.1. For ISO 286 choose the feature and class, such as internal H7 or external h6.DistributionStatistical model of the actual size. Normal: typical centred production, with tolerance limits treated as ±3σ by default. Uniform: every value inside the limits is equally likely. Triangular: values near the centre are more likely. A custom σ overrides automatic derivation.
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Simulation and target range
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Analysis

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Define dimensions and run the analysis.

Worst Case

Guaranteed limits

Every dimension is combined at its least favorable limit. The method requires no distribution assumption.

RSS / Monte Carlo

Statistical prediction

RSS assumes independent dimensions. Monte Carlo models the selected distributions; correlations, process drift, and measurement uncertainty are explicitly excluded from version 1.0.

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Determine an ISO 286 single-size tolerance →