TOOLSFOR FACTORIES

Engineering / WORKSHEET 10

Tolerance stack-up calculator

Add positively and negatively directed dimensions to estimate assembly extremes. Compare conservative worst-case limits with a statistical RSS estimate.

Output
Nominal stack, worst-case minimum and maximum, total span, and RSS minimum and maximum.
Processing
In this browser only
Cost
Free · no account

LIVE WORKSHEET

Define the dimension chain

Runs locally

Dimension chain

Inputs and results stay in this browser. Verify important outputs independently.

APPLICATION NOTES

Use the result on the floor

Calculate nominal, worst-case, and root-sum-square dimensional stack results from bilateral component tolerances. Keep the input boundary, unit definitions, and time period attached to any recorded result so another person can reproduce it.

Useful for

  • Screen a simple one-dimensional assembly chain.
  • Compare worst-case and RSS tolerance accumulation.
  • Document the dimensions included in a preliminary stack.

MODEL BOUNDARY

Assumptions and limitations

Assumptions

  • All dimensions are one-dimensional, linear, and use the same unit.
  • Plus and minus tolerance entries are non-negative magnitudes.
  • RSS assumes independent, centered contributors when interpreted statistically.

Limitations

  • RSS is not a guaranteed limit and no process capability or distribution is modeled.
  • The tool does not handle geometric tolerancing, thermal effects, datum shift, nonlinear geometry, correlation, or Monte Carlo analysis.

DECISION CHECK

Verify before changing the process

This is a screening calculation, not design release evidence. Have a qualified engineer verify the loop, signs, GD&T, statistical assumptions, safety factors, and drawing requirements.

REFERENCE

Frequently asked questions

What is worst-case stack-up?

It combines each contributor at the limit that produces the smallest or largest possible assembly result.

When is RSS appropriate?

RSS may be useful when contributors are independent and statistically centered. Confirm those assumptions and required confidence before relying on it.

How does a negative direction work?

A negative dimension subtracts its nominal value. Its plus component drives the stack downward and its minus component drives the stack upward.

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