Shaft and Hole Fit Calculator
The maximum and minimum clearance — or interference — between a hole and a shaft from their nominal size and tolerance deviations, and what kind of fit that makes.
A hole and shaft are each made to a size range: nominal plus an upper and lower deviation.
How the shaft and hole fit calculator works
A hole and shaft are each made to a size range: nominal plus an upper and lower deviation. The loosest case pairs the biggest hole with the smallest shaft; the tightest pairs the smallest hole with the biggest shaft. If both are positive the fit is a clearance fit (the shaft turns freely); both negative is an interference (press) fit; one of each is a transition fit that may go either way. Enter deviations in micrometers as they appear on a drawing — H7/g6 for a 50 mm shaft is +25/0 and −9/−25.
Formula: max clearance = hole max − shaft min; min clearance = hole min − shaft max
Worked examples
| Inputs | Fit | Note |
|---|---|---|
| 50 H7/g6: +25/0 and −9/−25 | clearance fit | clearance 9 to 50 µm |
| 50 H7/p6: +25/0 and +42/+26 | interference (press) fit | interference 1 to 42 µm |
| 50 H7/k6: +25/0 and +18/+2 | transition fit | transition |
FAQFrequently asked questions
What do H7/g6 and the other codes mean?
ISO 286 letters give the position of the tolerance band (H is a hole starting at zero, g a shaft just below the nominal, p a shaft above it) and numbers give the grade (width). The deviations for a given size are tabulated; enter them here.
Which fit do I want?
H7/g6 or H7/f7 for shafts that turn in bushes; H7/h6 for parts that slide or locate; H7/k6 or n6 for keyed gears that must not rattle; H7/p6 or s6 for permanent press fits. Bearings have their own tables.
Does temperature matter?
Yes — a steel shaft in an aluminium housing loses clearance as it heats, because aluminium expands twice as fast. Design the fit for the operating temperature and check it cold.
What is a transition fit?
One where the tolerance bands overlap: a given pair of parts may have a little clearance or a little interference. Used for locating parts that are assembled and taken apart with a light press.
Where these figures come from
- Nakajima (1988) — Introduction to TPM — the origin of Overall Equipment Effectiveness and its six big losses
- OSHA — the US workplace safety administration
Last checked: September 2026. Definitions follow standard operations-management practice; where plants commonly differ, the page says so.