Fareed Mohmed · Engineering
Shaft & Housing Fit Calculator for Bearings
Locate · Fit · Mount
Tell it which ring carries the rotating load, how heavy the load is, and the bore size — it recommends a shaft fit and a housing bore fit class, with the reasoning behind each.
This is general, widely-published starting-point guidance, not a substitute for your bearing manufacturer's own fit recommendation table, which also accounts for internal clearance class, operating temperature and specific bearing series.
Find the Recommended Fits
Recommended Shaft Fit
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Recommended Housing Bore Fit
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Explanatory Notes
The rule that drives everything here: tight on the rotating-load ring
Whichever ring turns relative to the direction of the applied load has to grip its seat tightly enough that it can't creep around — a loose ring under a rotating load slowly walks, wearing both the ring bore and the shaft or housing surface. The ring that's stationary relative to the load doesn't have this problem and can use a much looser fit, which also makes mounting and dismounting far easier.
Why the housing fit is usually looser than the shaft fit
In the ordinary case — a rotating shaft in a stationary housing — the shaft (inner ring) carries the rotating load and needs the tight fit, while the housing (outer ring) is the stationary-load ring and gets a clearance fit. That clearance fit on the non-locating bearing is also what lets the outer ring float axially as the shaft grows with temperature, without the whole assembly working against itself.
An interference fit tightens the bearing's own internal clearance
Pressing a ring onto an interference fit slightly expands (shaft fit) or slightly compresses (housing fit) that ring, which reduces the bearing's internal radial clearance. A bearing with normal (CN) clearance mounted with a heavy interference fit can end up preloaded — this is exactly why manufacturers offer C3/C4 (larger internal clearance) bearings specifically for tight interference-fit mountings.
Related tools
To first identify which bearing type suits the application, see the Bearing Type Selector, and to shortlist a standard-series bearing, the Bearing Size Finder. To verify the bearing's load and life once it's selected, see the Bearing Load, Life & Static Capacity Calculator.