GD&T MMC Bonus Tolerance Calculator

Compute the bonus geometric tolerance available when a feature-of-size departs from Maximum Material Condition (MMC), per ASME Y14.5.

GD&T · ASME Y14.5 MAXIMUM MATERIAL CONDITION

GD&T MMC Bonus Tolerance Calculator

Computes the bonus geometric tolerance available when a feature-of-size departs from Maximum Material Condition (MMC), per ASME Y14.5.

Feature Type

MMC Size
[Inches]

Actual Measured Size
[Inches]

Stated Position Tolerance (at MMC)
[Inches, diameter]

Total Allowable Position Tolerance

⌀0.017″

Bonus tolerance: 0.007″

✔
Bonus tolerance applies only when the drawing callout specifies MMC (Ⓜ) for this feature.

Engineering Model (ASME Y14.5 MMC bonus tolerance)

Standard Reference
ASME Y14.5 defines Maximum Material Condition (MMC) bonus tolerance for features of size. This calculator applies the standard bonus-tolerance rule directly — it is a documented ASME concept, not a simplified approximation.

Calculation Method
Bonus = |Actual Size − MMC Size| · Total Tolerance = Stated Tolerance + Bonus

Assumptions & Limitations

Only applies when the position (or other geometric) tolerance callout explicitly references MMC (Ⓜ) — regardless-of-feature-size (RFS, the default with no modifier) gets no bonus tolerance.
Does not include datum shift bonus tolerance from datum features that also reference MMC — this is a common additional bonus this tool does not compute.
Assumes the actual size is within the specified size tolerance (between MMC and LMC) — verify separately that the feature’s size itself is in tolerance.

STATIC REFERENCE DATA

Reference: Bonus Tolerance Examples

Precomputed values from the exact formula used above — useful as a quick lookup without re-entering inputs.

Feature	MMC Size	Actual Size	Stated Tol.	Bonus	Total Allowable
Hole (calculator default)	0.495″	0.502″	0.010″	0.007″	⌀0.017″
Hole, at MMC (no departure)	0.495″	0.495″	0.010″	0.000″	⌀0.010″
Hole, near LMC	0.495″	0.505″	0.010″	0.010″	⌀0.020″
Shaft, departed toward LMC	0.505″	0.498″	0.010″	0.007″	⌀0.017″

WORKED EXAMPLE

Checking a Bracket Hole Against Its Position Callout

A bracket hole is specified ⌀0.500 ± 0.005 with a position tolerance of ⌀0.010 at MMC. Inspection measures the actual hole at ⌀0.502. Does the part pass?

For a hole, MMC = the smallest allowed diameter (most material) = 0.500 − 0.005 = 0.495″.
Bonus tolerance = |Actual − MMC| = |0.502 − 0.495| = 0.007″.
Total allowable position tolerance = 0.010 + 0.007 = ⌀0.017″.
If the hole’s measured position deviation is within ⌀0.017″ of true position, the part passes — even though the stated callout was only ⌀0.010″, because the hole came in oversized (away from MMC) and earned bonus tolerance.

Related reading: Metallurgy & Quality Control →