GD&T True Position Calculator

Compute GD&T true position from measured X/Y deviation, with bonus tolerance at MMC, and pass/fail the feature.

True position converts a feature’s X/Y location error into a diameter that must fit inside the print’s tolerance zone.

At maximum material condition, a bonus tolerance is added as the hole grows away from MMC, so a slightly mislocated but larger hole can still pass.

Formula: Position = 2 × √(ΔX² + ΔY²)

Worked Example

  1. A hole is off by ΔX = 0.003 in and ΔY = 0.004 in.
  2. Position = 2 × √(0.003² + 0.004²) = 2 × 0.005 = 0.010 in diameter.
  3. It passes a 0.012 in positional tolerance.

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