Tolerance Stack Up Calculator __exclusive__ May 2026

Worst-case or RSS? Learn how to build a tolerance stack-up calculator in Excel or use our free web tool to predict assembly fit before you cut metal.

Stop Guessing: How to Use a Tolerance Stack-Up Calculator (Free Template Inside) tolerance stack up calculator

Assign a “+” if the dimension increases the gap/stack, “-” if it decreases. Worst-case or RSS

Pick one critical gap in your current assembly. Build the Excel sheet above. Compare worst-case vs RSS. You’ll be surprised how often your initial tolerances are either too tight (expensive) or too loose (non-functional). Pick one critical gap in your current assembly

The culprit? .

| Method | Formula (for additive tolerances) | Best for | |--------|----------------------------------|-----------| | | (T_total = \sum \vert T_i \vert) | Safety-critical, low volume | | Root Sum Square (RSS) | (T_total = \sqrt\sum T_i^2) | High-volume manufacturing (Cpk≥1.0) | Rule of thumb: Use RSS when you have 4+ parts in the stack and assume normal distribution. Use worst-case when human life or mandatory clearance is at stake. How to Build a Basic Calculator in Excel (5 Steps) You don’t need expensive software. Here is a manual setup: