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Calculate bonus tolerance with our GD&T Bonus Tolerance calculator. Find MMC, LMC, true position, hole, and shaft tolerance with easy steps.
Bonus Tolerance calculator helps you find extra GD&T tolerance with ease. It shows how much extra tolerance a feature can gain. This can help with part checks and design work.
Our calculator uses the feature size, MMC or RFS, and set tolerance. It can handle holes and shafts. It also gives the total allowed tolerance.
The bonus tolerance formula depends on the feature and modifier.
For a hole at MMC:
Bonus Tolerance = Actual Hole Size − MMC Size
For a shaft or pin at MMC:
Bonus Tolerance = MMC Size − Actual Size
If the callout uses RFS, bonus tolerance is zero.
The total tolerance uses this formula:
Total Tolerance = Set Geometric Tolerance + Bonus Tolerance
Think of it like extra room in a box. The more the feature moves from MMC, the more room you may gain.
MMC means Maximum Material Condition. It means the feature has the most material.
For a hole, MMC is the smallest hole size.
For a shaft, MMC is the largest shaft size.
For example, a hole has an MMC size of 10 mm. Its actual size is 10.20 mm.
Bonus tolerance is:
10.20 − 10.00 = 0.20 mm
So, the bonus tolerance is 0.20 mm.
LMC means Least Material Condition. LMC can also give bonus tolerance when the GD&T callout uses the LMC modifier.
For a hole, LMC is the largest hole size.
For a shaft, LMC is the smallest shaft size.
The same basic idea applies. You find the size change from LMC. Then, you add that amount to the stated geometric tolerance.
Always check the feature type and drawing callout first. This keeps the result correct.
You can use our GD&T bonus tolerance calculator in a few quick steps.
For true position, the same size rule applies when the position callout uses MMC.
Let's use a simple hole example.
The hole has these values:
First, find the bonus tolerance.
Bonus Tolerance = Actual Size − MMC Size
Bonus Tolerance = 20.25 − 20.00
Bonus Tolerance = 0.25 mm
Now add the bonus to the true position tolerance.
Total Tolerance = 0.10 + 0.25
Total Tolerance = 0.35 mm
So, the hole gains 0.25 mm of bonus tolerance. The total true position tolerance becomes 0.35 mm.
This is how a true position MMC bonus tolerance calculator works.
Now let's look at a shaft.
Suppose the shaft has:
For a shaft, use:
Bonus Tolerance = MMC Size − Actual Size
Bonus Tolerance = 10.00 − 9.80
Bonus Tolerance = 0.20 mm
Then:
Total Tolerance = 0.10 + 0.20
Total Tolerance = 0.30 mm
So, the shaft gets 0.20 mm of bonus tolerance.
A Bonus Tolerance calculator makes GD&T size checks much easier. You only need the right feature size and tolerance data.
For MMC, size growth away from MMC can give extra tolerance. For RFS, the bonus stays at zero.
Use the calculator to check holes, shafts, and true position values. It can save time and reduce math errors.
For a hole at MMC, subtract MMC size from actual size.
Bonus Tolerance = Actual Size − MMC Size
For a shaft, subtract actual size from MMC size.
Bonus Tolerance = MMC Size − Actual Size
MMC bonus tolerance is extra geometric tolerance gained as a feature moves away from MMC.
No. RFS does not give bonus tolerance. The bonus stays at zero.
Yes. A true position MMC bonus tolerance calculator can find the extra position tolerance gained from feature size.
For a hole at MMC:
Bonus Tolerance = Actual Hole Size − MMC Size
A larger hole can gain more bonus tolerance.
For a shaft at MMC:
Bonus Tolerance = MMC Size − Actual Shaft Size
A smaller shaft can gain more bonus tolerance.
Yes, if the drawing uses an LMC modifier. The key is to use the correct LMC size and feature direction.
Bonus tolerance adds to the stated position tolerance. Thus, a feature can have more position room as its size moves away from MMC.