--- type: "calculator" name: "ISO 286 Limits & Fits Calculator" standard: "ISO 286-1 / ISO 286-2" verified: "August 1, 2026" url: https://shopmath.org/calculators/iso-fit --- # ISO 286 Limits & Fits Calculator H7/g6 at Ø25 mm is a clearance fit: the hole runs 25.0000–25.0210 mm and the shaft 24.9800–24.9930 mm, leaving 7–41 µm of clearance. Any size from 1 to 500 mm and any tabulated letter and grade works the same way. ## Inputs | Input | Range | Notes | | --- | --- | --- | | Nominal size | 1–500 mm | Above 500 mm the standard uses a different tolerance factor entirely; the calculator refuses rather than extrapolating. | | Named fit | any of the sixteen standard hole-basis and shaft-basis fits | A preset fills both designations at once. | | Hole and shaft designation | letter plus IT grade, restricted to the pairs the tables can answer | The letter list is derived from the deviation table, so a letter can never be offered at a grade the tables do not carry. | ## Worked example — H7/g6 at Ø25 mm - **Nominal size**: 25 mm - **Hole**: H7: 0 to 21 µm → 25.0000–25.0210 mm - **Shaft**: g6: -20 to -7 µm → 24.9800–24.9930 mm - **Minimum clearance**: 7 µm - **Maximum clearance**: 41 µm - **Classification**: clearance ```text max clearance = hole max − shaft min = 21 − (-20) = 41 µm min clearance = hole min − shaft max = 0 − (-7) = 7 µm ``` Both deviations are read out of the compiled ISO 286-2 table. Nothing is computed from the ISO 286-1 tolerance formula, which misses the published table by up to 13.26%. ## The 16 named fits at Ø25 mm | Fit | Class | Min clearance (µm) | Max clearance (µm) | Role | | --- | --- | --- | --- | --- | | [H7/h6](https://shopmath.org/fits/h7-h6.md) | clearance | 0 | 34 | Locational clearance. Assembles by hand, no free movement intended. | | [H11/c11](https://shopmath.org/fits/h11-c11.md) | clearance | 110 | 370 | Loose running. Wide commercial tolerances, large clearance for dirt, paint and thermal growth. | | [H7/g6](https://shopmath.org/fits/h7-g6.md) | clearance | 7 | 41 | Sliding. Locates accurately, still moves and turns freely. | | [H8/e8](https://shopmath.org/fits/h8-e8.md) | clearance | 40 | 106 | Running fit with room for a lubricant film at speed. | | [H8/f7](https://shopmath.org/fits/h8-f7.md) | clearance | 20 | 74 | Close running. The general-purpose lubricated journal fit. | | [H9/d9](https://shopmath.org/fits/h9-d9.md) | clearance | 65 | 169 | Free running. Good where accuracy is not essential and clearance can be generous. | | [H7/p6](https://shopmath.org/fits/h7-p6.md) | interference | -35 | -1 | Locational interference. Rigid location in steel without the load capacity of a drive fit. | | [H7/r6](https://shopmath.org/fits/h7-r6.md) | interference | -41 | -7 | Medium drive. The joint itself carries load. | | [H7/k6](https://shopmath.org/fits/h7-k6.md) | transition | -15 | 19 | Locational transition. Accurate location, assembles with light force. | | [H7/m6](https://shopmath.org/fits/h7-m6.md) | transition | -21 | 13 | Locational transition, tighter than k6. | | [H7/n6](https://shopmath.org/fits/h7-n6.md) | transition | -28 | 6 | Tight transition. Usually a press job. | | [F8/h7](https://shopmath.org/fits/f8-h7.md) | clearance | 20 | 74 | Close running, shaft basis. | | [G7/h6](https://shopmath.org/fits/g7-h6.md) | clearance | 7 | 41 | Sliding, shaft basis. The h6 shaft is the reference and the hole carries the clearance. | | [P7/h6](https://shopmath.org/fits/p7-h6.md) | interference | -35 | -1 | Locational interference, shaft basis. | | [K7/h6](https://shopmath.org/fits/k7-h6.md) | transition | -15 | 19 | Locational transition, shaft basis. | | [N7/h6](https://shopmath.org/fits/n7-h6.md) | transition | -28 | 6 | Tight transition, shaft basis. | A negative clearance is interference. The ladder runs from the loosest running fit to the heaviest drive fit; the calculator will classify any pair, including ones no published table lists. ## Sources and Method for the ISO 286 Limits & Fits Calculator ### ISO 286 tables - **Source**: saucecode/ISO286 (LGPL-2.1) + parkergreene/isofits (MIT), cross-checked cell-for-cell - **Method**: compiled - **Verified against**: fits-iso286: 2067 checks passed across 3 harness(es) ### Formulas **Limits of size from the tabulated deviations** ```text hole max = D + ES ÷ 1000 hole min = D + EI ÷ 1000 shaft max = D + es ÷ 1000 shaft min = D + ei ÷ 1000 D = nominal size (mm) ES, EI = upper and lower deviation of the hole (µm) es, ei = upper and lower deviation of the shaft (µm) ``` **The deviation the table does not print** ```text holes A–H: ES = EI + IT holes J–R: EI = ES − IT shafts a–h: ei = es − IT shafts j–r: es = ei + IT ``` _ISO 286-2 tabulates only the deviation nearer the zero line; the other end of the zone is that value plus or minus the standard tolerance for the grade._ **Clearance and the classification** ```text max clearance = hole max − shaft min = ES − ei min clearance = hole min − shaft max = EI − es min ≥ 0 -> clearance fit max ≤ 0 -> interference fit otherwise -> transition fit ``` _A negative clearance is interference. This is why the calculator can classify a pair that appears in no published fit table._ ### Assumptions - Values are COMPILED from two independent open datasets that agree cell-for-cell, not computed. The ISO 286-1 formula deviates from the published table by up to 13.26% and is retained as a validation harness only. - Size bands are ranges, stated as 'over X, up to and including Y'. A 30 mm feature uses the 18–30 band and a 30.01 mm feature uses 30–50. Nothing is interpolated between bands, because the standard does not interpolate. - Coverage is 1–500 mm and grades IT5–IT12. Sizes above 500 mm use a different tolerance factor entirely and are not in these tables; the calculator refuses rather than extrapolating. - Shaft and hole letters s, t and u — and the fits H7/s6, H7/t6, H7/u6 — are excluded. No free source was available and the formula has an undetermined step constant, so shipping them would mean shipping a guess. - Deviations for the letters j to r and J to R depend on the tolerance grade, and only the grades that are tabulated are offered. The composite letters CD, EF and FG exist only at the small end and disappear above 10 mm. - These are dimensional limits only. Surface finish, form error, temperature and the assembly method all affect a real fit and none of them are in this calculation. - ISO 286 tables scope: COMPILED not computed: the ISO 286-1 formula deviates up to 13.26% from the table and is used only as a harness (warn >5%, fail >15%). EXCLUDED: shaft/hole letters s, t, u and the fits H7/s6, H7/t6, H7/u6 — no free source and an undetermined step constant in the formula. **Data last verified**: August 1, 2026 ## Related pages - Per-designation limits: [ISO 286 fit reference](https://shopmath.org/fits.md) - Lookup version: [ISO 286 tolerance chart](https://shopmath.org/charts/iso-tolerances.md) - All calculators: [Machining calculators](https://shopmath.org/calculators.md) --- *Source: [ShopMath](https://shopmath.org/calculators/iso-fit) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*