Engineering Fits Calculator
ISO 286 tolerance calculator for hole-basis fits. Calculate clearance, transition, and interference fits with visualization.
Inputs
H = Hole basis (EI = 0)
Basic size D in mm (1-500 mm)
Select a fit and enter dimensions, then click Calculate.
Tolerance Zone Diagram
ISO 286 Tolerance Calculations
The ISO system uses a standard tolerance unit i that scales with diameter:
\[ i = 0.45 \cdot D^{1/3} + 0.001 \cdot D \quad \text{(μm)} \]
IT grade tolerances are multiples of this unit:
\[ IT_n = k_n \cdot i \]
Where \(k_n\) is the grade multiplier (e.g., IT7 = 16i, IT6 = 10i)
Size Limits
\[ D_{hole,max} = D + ES \quad,\quad D_{hole,min} = D + EI \]
\[ D_{shaft,max} = D + es \quad,\quad D_{shaft,min} = D + ei \]
Clearance / Interference
\[ C_{min} = D_{hole,min} - D_{shaft,max} = EI - es \]
\[ C_{max} = D_{hole,max} - D_{shaft,min} = ES - ei \]
Positive = clearance, Negative = interference
Clearance Fits (a-h)
Always positive clearance - parts move/slide freely
H7/h6: Locational clearance
H7/g6: Sliding fit
H8/f7: Close running fit
H7/g6: Sliding fit
H8/f7: Close running fit
Transition Fits (js-n)
May have clearance or interference depending on actual sizes
H7/js6: Snug fit, easy assembly
H7/k6: Push fit with light force
H7/n6: Tight, probable interference
H7/k6: Push fit with light force
H7/n6: Tight, probable interference
Interference Fits (p-u)
Always interference - requires press or thermal assembly
H7/p6: Light press fit
H7/s6: Heavy press fit
H7/u6: Shrink fit
H7/s6: Heavy press fit
H7/u6: Shrink fit
Surface Finish Recommendations
| Fit Type | Hole Ra (μm) | Shaft Ra (μm) |
|---|---|---|
| Loose Running | 3.2 - 6.3 | 1.6 - 3.2 |
| Running/Sliding | 1.6 - 3.2 | 0.8 - 1.6 |
| Transition | 0.8 - 1.6 | 0.4 - 0.8 |
| Interference | 0.8 - 1.6 | 0.4 - 0.8 |