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Tolerance Stack-Up Calculator

This stack-up calculator combines signed nominal dimensions and bilateral tolerances. It reports deterministic worst case and statistical RSS results so the assumptions remain visible.

Run the calculation

Your data stays in this browser. No measurements are uploaded.

  1. 1 Enter data
  2. 2 Review results
  3. 3 Take action

Study inputs

Use one linear contributor per row. Enter + or − in the third column.

Ready for your data

Complete the inputs or load the worked example. Results will include the primary decision, interpretation and supporting metrics.

Worked example

For +20.00 ±0.05, +10.00 ±0.03 and −5.00 ±0.02 mm, nominal is 25.00 mm, worst-case tolerance is ±0.10 mm and RSS is approximately ±0.062 mm.

Load the example in the calculator

Formula and methodology

  1. Signed nominal dimensions are added algebraically.
  2. Worst-case tolerance is the sum of absolute bilateral tolerances.
  3. RSS assumes independent, centred contributors and combines tolerances by root-sum-square.
Nominal = Σ(si × xi)Worst case = ±Σ|ti|RSS = ±√Σ(ti²)

How to interpret the result

  • Worst case protects against every contributor reaching its adverse limit simultaneously.
  • RSS can be useful for independent stable distributions but does not guarantee assembly acceptance.
  • Datum scheme, geometric tolerances and correlations may require a full variation model.

Common errors and limitations

  • Dropping the sign of a closing dimension.
  • Using RSS without evidence of independence and centring.
  • Ignoring geometric variation, thermal effects or assembly deformation.

Turn the calculation into an engineering decision

Share the drawing, process conditions and result context. AccuTouch can review the measurement, fixture, SPC or automation starting point.

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Frequently asked questions

Worst case or RSS?

Use worst case when guaranteed interchangeability is required. Use RSS only when its statistical assumptions are justified and risk is accepted.

Does this calculate geometric tolerances?

No. It handles a one-dimensional bilateral linear stack only.

Can unilateral tolerances be entered?

Convert them to a centred nominal and bilateral equivalent before using this version, documenting the transformation.

Technical references

Use the current controlled standard or your organisation’s approved method where it differs from this screening tool.

Method content reviewed 13 August 2026. Independent technical approval is still required before production publication or use in a controlled quality procedure.