Calculator
Example Data Table
| Example | Nominal | Tolerance | Lower limit | Upper limit | Readings | Outside % |
|---|---|---|---|---|---|---|
| Small part length | 100 | ±2% | 98 | 102 | 99.8, 100.4, 97.6, 102.3 | 50% |
| Filled weight | 250 | -3, +5 absolute | 247 | 255 | 248, 252, 256, 246 | 50% |
| Direct limits | Not needed | Limits entered | 9.5 | 10.5 | 10.1, 9.4, 10.6, 9.8 | 50% |
Formula Used
Percent tolerance limits: Lower limit = Target × (1 − Lower tolerance ÷ 100). Upper limit = Target × (1 + Upper tolerance ÷ 100).
Absolute tolerance limits: Lower limit = Target − Lower absolute tolerance. Upper limit = Target + Upper absolute tolerance.
Outside count: Outside count = Below lower limit + Above upper limit.
Percentage outside tolerance: Outside % = (Outside count ÷ Total measurements) × 100.
Inside percentage: Inside % = (Inside count ÷ Total measurements) × 100.
Deviation: Deviation = Measurement − Target.
Deviation percentage: Deviation % = (Deviation ÷ |Target|) × 100.
How to Use This Calculator
- Enter a batch name and inspector name if needed.
- Paste all measured values into the measurement box.
- Select the tolerance mode that matches your data.
- Enter the nominal value, tolerance values, or direct limits.
- Choose whether exact boundary values pass or fail.
- Press Calculate to see the outside percentage.
- Use CSV or PDF buttons to save a report.
Article
Why Tolerance Percentage Matters
A tolerance report shows how often measured work misses the accepted range. It is simple, but it is powerful. A high outside percentage points to drift, tool wear, poor setup, supplier variation, or weak inspection rules. A low percentage suggests stable work, but it still needs review. One bad part can matter when safety, cost, or fit is critical.
What This Calculator Checks
This calculator compares each value against a lower and upper limit. You can enter limits directly, use a nominal value with percentage tolerance, or use absolute tolerance. The tool then counts values below tolerance, above tolerance, inside tolerance, and outside tolerance. It also reports the outside percentage, inside percentage, average, minimum, maximum, and standard deviation. These extra values help you see both pass rate and spread.
Using the Result for Decisions
The outside percentage is best used with context. A batch with ten readings can change quickly after one failure. A batch with thousands of readings gives steadier evidence. Compare the rate with your acceptance plan, customer agreement, or internal quality target. If failures cluster above the upper limit, the process may be centered too high. If failures cluster below the lower limit, it may be centered too low. If failures appear on both sides, variation may be too wide.
Good Data Habits
Use one unit for every reading. Do not mix millimeters with inches, grams with kilograms, or volts with millivolts. Remove notes from the value list. Keep only numbers, commas, spaces, or new lines. Record the instrument, operator, lot, and date outside the number list. These details make later audits easier.
Improving the Process
After finding the outside percentage, check causes before changing limits. Review calibration, sampling method, material lot, environment, and machine setup. Then repeat the calculation with fresh readings. A lower outside rate after correction confirms improvement. Export the CSV or PDF report to keep a clear record.
When to Investigate
Investigate any sudden rise in failures, even when the final rate still looks acceptable. Trend charts, run order, and subgroup notes can reveal changes hidden by one summary number. Stable tolerance control needs measurement discipline, realistic limits, and regular review by people close to the process daily.
FAQs
What does outside tolerance mean?
It means a measurement is lower than the accepted lower limit or higher than the accepted upper limit. The calculator counts those values as failures unless your boundary rule allows exact limits.
Can I use unequal tolerances?
Yes. You can enter different lower and upper percentages. You can also use different absolute tolerances. This helps with specifications such as -1% and +3%.
What happens when a value equals the limit?
The boundary rule controls this. Choose “Limits are acceptable” to count exact limit values as inside tolerance. Choose “Limits are failures” for stricter checking.
Do I need a nominal target?
You need a nominal target for percent and absolute tolerance modes. You do not need it when using direct lower and upper specification limits.
Can I paste values from a spreadsheet?
Yes. Paste values separated by spaces, commas, tabs, or new lines. The calculator extracts numeric readings and ignores normal separators.
Why is standard deviation included?
Standard deviation shows how spread out the measurements are. A batch may have few failures but still show high variation. That can warn you before more values fail.
What should I do with a high outside percentage?
Check calibration, setup, raw material, operator method, environment, and sampling method. Do not widen limits without confirming that the specification allows it.
Which export should I use?
Use CSV for full data review in spreadsheets. Use PDF for a compact summary report that is easier to share or attach to an audit record.