ISO 286 fits and tolerances calculator

When to use which fit

Almost every fit starts with H. That is the hole-basis system: the hole keeps a lower deviation of zero and the type of fit is set by the shaft. The reason is cost — standard drilling and reaming tools give an H hole by themselves, while a shaft can be turned or ground to any size, so one reamer covers every fit.

The pairs below are the ones in common use, from the loosest to the tightest:

Fit	Type	What it is used for
H11/h11	clearance, coarse	Welded and soldered parts, spacer sleeves, parts clamped on shafts — wherever accuracy does not matter.
H7/f7	clearance	Plain bearings and slideways — continuous running with an oil film.
H7/g6	clearance	Connecting-rod plain bearings, guide pins and dowels. The part has to turn or slide, but without perceptible play.
H7/h6	clearance, the tightest	Joints moved by hand after oiling: sealing rings, guideways, hubs taken apart with a spanner.
H7/k6	transition	Pulleys and flywheels on shafts, hand levers, dowels, bolts and locating pins. Holds its position and still comes apart.
H7/m6	transition	Belt pulleys and gears on shafts secured against axial movement, pins and locating dowels.
H7/n6	transition, close to interference	Gear rims in hubs, bushings in housings, wheels and couplings on shafts, levers and cranks.
H7/p6	interference	Gears on shafts of machines under varying and shock loads, bearing bushings, pins, retaining rings.
H7/r6	interference	Pressed joints: gears on shafts, clutch discs, gear rims in hubs.
H7/s6	interference, heavy	Joints assembled under a press or shrunk on, where the connection has to hold by interference alone.

The rule of thumb that follows: the more the joint has to move, the further left (f, g, h); the harder it has to hold, the further right (p, r, s). The middle — k, m, n — covers the cases of “it must sit exactly where it sits, but I want to take it apart one day”.

Rolling bearings are a separate case

⚠️ Do not pick a bearing seat from the table above. Bearing makers publish their own recommendations for the shaft and the housing, and the catalogue of the actual bearing prevails. SKF and NSK agree almost exactly here — what follows is their common ground.

One question decides it: does the load rotate relative to a given ring, or stand still? If the loaded zone travels around the ring, that ring must be an interference fit — otherwise it starts to creep, that is to turn slowly against the shaft or the housing, and wears the seat out. A ring under a load that stays in one place may be fitted more loosely, and often should be, so that it can move axially with thermal expansion.

Solid steel shaft, ball bearings

Condition	Shaft diameter	Shaft class
Rotating load on the inner ring — light or variable	up to 18 mm	js5
	18–100 mm	j6 / js6
	100–200 mm	k6
Rotating load, normal	up to 18 mm	js5 / j5
	18–100 mm	k5 (or k6)
	100–140 mm	m5 (or m6)
	140–200 mm	m6
Rotating load, heavy or shock	large diameters	n6, p6, r6
Stationary load, the ring has to be free to move	—	g6
Stationary load, no axial movement needed	—	h6

Cast iron or steel housing

Condition	Housing class
Rotating load on the outer ring — heavy, shock loads, thin-walled housing	P7
Rotating load, normal to heavy	N7
Rotating load, light or variable	M7
Stationary load, the outer ring has to be free to move	H7, H8 or G7

The table applies to cast iron and steel housings. In light-alloy housings the interference should be tighter than shown above.

Not sure what to put on the drawing? Tell us what the part has to do and whether it has to move — we will pick the fit and tell you what can be machined. biuro@hardpower.pl

Sources behind this guide

Types of fit and the hole-basis system: Technische Antriebselemente, “ISO Fits H7/H6” · Portal Narzędzi, “Akademia ślusarstwa, part 6” · R. Grzejda, “Podstawy tolerancji i pasowań”, West Pomeranian University of Technology, Szczecin 2025.
Table of applications: Podstawy Konstrukcji Maszyn, “Dobór pasowań wymiarów”, confirmed independently against Technische Antriebselemente.
Bearings: SKF, “Seat tolerances for standard conditions” · NSK, “Fits and Internal Clearance” and the NSK bearing catalogue, section 9 “Fits”, tables 9.2 and 9.4. All sources read on 21 September 2026.
A statement enters these tables only when two independent sources give it identically. The deviation values are calculated from the tables of ISO 286-2:2010. This guide is a workshop aid — the wording of the standard prevails, and for bearings the maker’s catalogue does.