🎯 True Position Calculator
Enter the measured X and Y deviation from the true (nominal) location and your position tolerance to check a feature’s true position against a GD&T callout.
What This Calculator Does
In geometric dimensioning and tolerancing (GD&T), true position measures how far a feature’s actual center is from its theoretically exact (true) location, expressed as a single diameter value that must fit within a specified tolerance zone.
The Formula
True position is calculated as 2 times the square root of the sum of the squared X and Y deviations: TP = 2 x sqrt(dx^2 + dy^2). This doubles the radial distance from nominal because the position tolerance is defined as a diameter, not a radius. The result is then compared against the drawing’s stated position tolerance to see how much of the allowable zone has been used.
Good to Know
- A part passes when the calculated true position is less than or equal to the stated position tolerance; a negative “remaining tolerance” means the feature is out of tolerance.
- This calculator covers the basic (RFS) true position formula and does not include bonus tolerance from MMC/LMC modifiers — consult your GD&T drawing and standard (ASME Y14.5) for those cases.