Engineering Limit Inputs
Use signed tolerances. Example: +0.08 and -0.04.
Example Data Table
| Part | Nominal | Upper Tol | Lower Tol | Measured | Upper Limit | Lower Limit | Status |
|---|---|---|---|---|---|---|---|
| Shaft A | 25.000 mm | 0.030 mm | -0.020 mm | 25.010 mm | 25.030 mm | 24.980 mm | PASS |
| Pin B | 12.500 mm | 0.015 mm | -0.015 mm | 12.520 mm | 12.515 mm | 12.485 mm | FAIL |
| Sleeve C | 40.000 mm | 0.050 mm | -0.030 mm | 39.980 mm | 40.050 mm | 39.970 mm | PASS |
| Bushing D | 18.750 mm | 0.025 mm | -0.010 mm | 18.742 mm | 18.775 mm | 18.740 mm | PASS |
Formula Used
Upper Limit = Nominal Size + Upper Tolerance
Lower Limit = Nominal Size + Lower Tolerance
Total Tolerance Width = Upper Limit - Lower Limit
Deviation = Measured Value - Nominal Size
Band Position (%) = ((Measured - Lower Limit) / Tolerance Width) × 100
Pass Condition = Lower Limit ≤ Measured Value ≤ Upper Limit
If tolerance inputs are reversed, the calculator normalizes them so the lower limit remains smaller than the upper limit.
How to Use This Calculator
- Enter the nominal dimension from the drawing or process sheet.
- Enter the upper and lower tolerances with their correct signs.
- Add the measured value from inspection or shop-floor data.
- Choose decimal precision and type the working unit label.
- Press Calculate Limits to view limits, status, metrics, and the graph.
- Use the CSV and PDF buttons to save the report.
Frequently Asked Questions
1. What are upper and lower limits in engineering?
Upper and lower limits define the largest and smallest acceptable finished dimensions. They are derived from a nominal value plus tolerance values. These limits help engineers judge whether a part, feature, or process output stays within specification.
2. How do nominal size and tolerance work together?
A nominal size is the target dimension. Tolerances describe allowed variation above and below that target. Add the upper tolerance to get the upper limit. Add the lower tolerance to get the lower limit.
3. Can I use different upper and lower tolerances?
Yes. Many drawings use bilateral tolerances, such as +0.05 and -0.03. This calculator accepts different upper and lower tolerance values, then shows the full allowable range and measured part position.
4. How does the pass or fail result work?
If a measured value sits between the lower and upper limits, it passes. If it falls below the lower limit or above the upper limit, it fails and needs review, sorting, or process correction.
5. What does tolerance width tell me?
Tolerance width is the distance between the upper and lower limits. A wider band allows more variation. A narrower band demands tighter control, better tooling, and more stable measurement conditions.
6. What if I enter tolerances in the wrong order?
Enter tolerances with the correct signs from the drawing. If values are reversed, the calculator normalizes them for the final range so the lower limit remains smaller than the upper limit.
7. Which units should I use?
Use the same unit for nominal size, tolerances, and measured value. Common choices include millimeters, inches, micrometers, or mils. The calculator keeps units consistent throughout the report and exports.
8. What does the plot show?
The graph shows the tolerance band as an allowable span. It also marks the nominal value, measured value, and both limits. This helps you see centering, available margin, and possible out-of-limit conditions quickly.