Calculator Inputs
Example Data Table
| Nominal | + Tol | - Tol | Measured | Process Mean | Std Dev | USL | LSL | Deviation | Cpk | Status |
|---|---|---|---|---|---|---|---|---|---|---|
| 25.000 mm | 0.080 mm | 0.050 mm | 25.030 mm | 25.010 mm | 0.015 mm | 25.080 mm | 24.950 mm | +0.030 mm | 1.333 | Within tolerance |
This sample represents an asymmetric bilateral tolerance where the positive and negative allowances differ.
Formula Used
This calculator combines direct inspection math with process capability indicators, helping quality teams evaluate both a single measurement and the wider process behavior.
How to Use This Calculator
- Enter the nominal dimension for the part or feature.
- Input the positive and negative tolerance values exactly as allowed by the drawing or specification.
- Enter the measured inspection result for the current part.
- Add process mean and process standard deviation if you also want Cp, Cpu, Cpl, Cpk, yield, and ppm estimates.
- Select the number of decimal places and confirm your unit label.
- Press the calculate button to display results, a tolerance graph, and CSV or PDF export options.
FAQs
1. What is bilateral tolerance?
Bilateral tolerance allows variation on both sides of a nominal dimension. The upper and lower limits may be equal or unequal, depending on the drawing requirement.
2. How is bilateral tolerance different from unilateral tolerance?
Bilateral tolerance permits movement above and below nominal. Unilateral tolerance allows variation in only one direction while keeping the other side fixed.
3. What does side tolerance used mean?
It shows how much of the relevant upper or lower allowance the measurement has consumed. This helps inspectors judge proximity to the nearest specification boundary.
4. Why are Cp and Cpk included?
Cp measures potential capability from spread alone. Cpk also considers process centering, making it more useful when the process mean is shifted from target.
5. What does a negative deviation mean?
A negative deviation means the measured value is below the nominal dimension. It may still be acceptable if it remains above the lower specification limit.
6. Can the nominal dimension differ from the specification midpoint?
Yes. That happens when the upper and lower tolerances are unequal. In that case, the midpoint shifts away from nominal and the specification becomes asymmetric.
7. Should I rely only on within tolerance status?
No. A part can pass today while the process still trends toward a limit. Capability metrics and remaining margin provide stronger control insight.
8. When is this calculator useful?
It is useful during incoming inspection, machining checks, first article review, production audits, process studies, and final quality acceptance decisions.