Measure unequal bilateral tolerance and disposition with confidence. Check limits, offsets, capability, and acceptance using structured calculations for daily inspection reviews.
| Nominal | +Tol | -Tol | USL | LSL | Actual | Disposition |
|---|---|---|---|---|---|---|
| 50.000 | 0.080 | 0.030 | 50.080 | 49.970 | 50.040 | 0.025 |
| 25.000 | 0.050 | 0.020 | 25.050 | 24.980 | 25.010 | 0.015 |
| 10.000 | 0.030 | 0.060 | 10.030 | 9.940 | 9.980 | -0.015 |
Unequal bilateral tolerance uses different upper and lower limits around the nominal size. The upper specification limit equals nominal plus upper tolerance. The lower specification limit equals nominal minus lower tolerance.
USL = Nominal + Upper Tolerance
LSL = Nominal - Lower Tolerance
Total Tolerance = Upper Tolerance + Lower Tolerance
Zone Midpoint = (USL + LSL) / 2
Disposition = Zone Midpoint - Nominal
If the disposition is positive, the entire tolerance zone sits above the nominal center. If it is negative, the zone sits below the nominal center. This helps inspectors understand whether design intent favors one side.
When standard deviation is entered, the calculator also estimates capability. Cp compares total tolerance to spread. Cpu checks distance to the upper limit. Cpl checks distance to the lower limit. Cpk is the smaller of Cpu and Cpl.
Cp = (USL - LSL) / (6 × Standard Deviation)
Cpu = (USL - Mean) / (3 × Standard Deviation)
Cpl = (Mean - LSL) / (3 × Standard Deviation)
Cpk = min(Cpu, Cpl)
Enter the nominal size first. Add the positive upper tolerance and the positive lower tolerance magnitude. The calculator automatically places the lower side below nominal.
Enter the actual measured size or process mean. Add sample minimum and sample maximum if you want a quick range review. Enter standard deviation to estimate capability values.
Press the calculate button. The result appears above the form and below the header. Review the computed limits, total tolerance, midpoint, disposition, remaining margins, and capability data.
Use the CSV button to download key results into a spreadsheet. Use the PDF button to save the displayed result section for reporting or inspection records.
Unequal bilateral tolerance is common in quality control, machining, gauging, tooling, and assembly work. It lets designers assign a different allowable variation above nominal than below it. That is useful when one side affects function more than the other. A shaft, bore, groove, or feature may still fit correctly even when the tolerance zone is intentionally shifted.
Disposition describes that shift. In this calculator, disposition is the distance between the nominal size and the midpoint of the actual tolerance zone. When the midpoint is not equal to nominal, the zone is not centered. That means the part drawing accepts more movement in one direction. This is important during process review because the nominal dimension alone does not explain the true available room.
The calculator helps teams inspect both design intent and process behavior. It computes upper and lower specification limits, total tolerance, tolerance shares, and the unequal ratio. It also compares the actual value with both boundaries and shows remaining margin to each side. Those numbers help decide whether a process is running too close to one limit.
If standard deviation is available, capability metrics provide more insight. Cp shows potential fit. Cpk shows whether the process mean is positioned safely within the unequal zone. Together, the results support acceptance decisions, corrective action, and tolerance review during audits or production meetings.
It is a tolerance scheme with different allowable variation above and below nominal. One side may allow more movement because of fit, function, tooling, or assembly requirements.
Disposition is the shift between the nominal size and the midpoint of the tolerance zone. It shows whether the full allowable zone is biased upward or downward.
The form treats lower tolerance as a magnitude. The calculator automatically subtracts it from nominal. That reduces input mistakes and keeps the lower limit logic consistent.
The actual value passes when it lies between the lower specification limit and the upper specification limit, including the boundaries when your inspection rule allows it.
The midpoint shows the center of the allowed zone, not the nominal dimension. Comparing midpoint and nominal reveals whether the drawing intentionally favors one side.
Enter standard deviation when you want capability estimates such as Cp, Cpu, Cpl, and Cpk. These values help judge process spread and centering.
Yes. They provide a simple observed range check. They do not replace full capability analysis, but they help reviewers quickly compare actual spread with specification space.
Cpk includes process location relative to both limits. Cp only compares total tolerance with spread. A process can have a good Cp yet still run too close to one boundary.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.