True Position Calculator

Use this true position calculator to estimate how far a hole or shaft center is from its intended location. It also shows bonus tolerance planning for MMC and LMC style checks. This page also keeps the formula, examples, FAQs, and references close by so you can check the result with confidence.

What This True Position Calculator Helps You Do

True position variation = 2 × sqrt((TB - MB)^2 + (TC - MC)^2). Bonus tolerance is the difference between the actual feature size and the material condition size. Review the formula and examples below if you want to see how the result is derived.

This page is meant to give you a fast answer, but it also helps you double-check the math before you make a decision. Start with the inputs that you already know, run the calculation, and then compare the output with the formula, examples, and FAQs below so you can see whether the answer fits the situation you are modeling.

If the result looks off, the usual causes are a unit mismatch, a missing decimal, the wrong scenario, or a value that needs to be entered as a rate instead of a total. The notes on this page are designed to make those checks easy without forcing you to leave the calculator and search for context elsewhere.

  • Use the calculator first for a quick estimate.
  • Use the formula to understand how the result is built.
  • Use the examples to compare common use cases.
  • Use the references when the answer depends on a standard or assumption.

Common Checks

A quick result is useful, but the best result is one that still makes sense when you look at it a second time. If you are comparing scenarios, try changing one input at a time so you can see which variable has the biggest impact on the final answer. That makes it much easier to spot whether the calculation matches your expectations.

It also helps to keep the context of the problem in mind. A calculator can tell you the math, but you still need to decide whether the input represents a total, a rate, an average, or a category-specific assumption. When in doubt, start with a simple example from the page and scale up from there.

  • Check that every unit matches the rest of the problem.
  • Keep rates, totals, and averages separate.
  • Adjust one variable at a time when testing scenarios.
  • Use the smallest realistic input first, then scale upward.

Scenario Planning

This calculator is especially useful when you want a quick answer before you commit time, money, or effort. Try one baseline input set, then change a single number and compare the result so you can see how sensitive the answer is to that variable.

That makes the page useful for more than just arithmetic. It becomes a small decision aid that helps you compare options, test assumptions, and explain the final number with confidence when you need to share it with someone else.

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Result

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Quick Answer: True position variation = 2 × sqrt((TB - MB)^2 + (TC - MC)^2). Bonus tolerance is the difference between the actual feature size and the material condition size. Review the formula and examples below if you want to see how the result is derived.

How to Calculate True Position Calculator

  1. Enter the true position: Use the nominal coordinates from the drawing for the two datum directions.
  2. Enter the measured position: Use the observed part location from the inspection or layout.
  3. Add tolerance limits: Use the position tolerance and the relevant MMC or LMC size.
  4. Check the fit: Compare the variation and total tolerance before accepting the part.

True Position Calculator Formula

PV = 2 × sqrt((TB - MB)^2 + (TC - MC)^2)
Variable Meaning Unit
PV Position variation mm
TB True position on B mm
MB Measured position on B mm
TC True position on C mm
MC Measured position on C mm

Worked Examples

USA - Simple hole layout
  • TB: 50 mm
  • MB: 50.6 mm
  • TC: 25 mm
  • MC: 24.2 mm

Result: Position variation = 2.88 mm

The variation is easy to compare with a diameter-style tolerance zone.

UK - MMC bonus check
  • Position tolerance: 1 mm
  • Actual size: 10.2 mm
  • MMC size: 10 mm

Result: MMC total tolerance = 1.2 mm

A bigger hole or shaft can create useful bonus tolerance.

EU - LMC bonus check
  • Position tolerance: 1 mm
  • Actual size: 10.2 mm
  • LMC size: 10.6 mm

Result: LMC total tolerance = 1.4 mm

The total tolerance grows when the feature moves toward the least material condition.

GCC - Quick inspection
  • TB: 40 mm
  • MB: 39.4 mm
  • TC: 15 mm
  • MC: 14.8 mm

Result: Position variation = 1.26 mm

A quick two-axis check helps before you compare against the drawing limit.

How to Interpret Your Results

Range Meaning Action
Below tolerance The feature is likely acceptable Compare with the drawing and material condition.
Near tolerance The feature is close to the limit Double-check the datum setup and measurement method.
Above tolerance The feature may be out of spec Review the part before it moves to the next operation.

Frequently Asked Questions

It is the allowed variation of a feature's location relative to its nominal position.

The position tolerance is given as a diameter, so the radial distance is doubled for comparison.

MMC means maximum material condition, which is the size that contains the most material.

LMC means least material condition, which is the size that contains the least material.

Yes. The same position concept is useful for both internal and external features.
Planning note: This calculator is a planning and learning aid only. Inspection results should always be compared with the controlling drawing or standard.

References

Last reviewed: March 2026