Use this bolt hole clearance calculator to calculate the clearance between a bolt and a hole. The calculator determines diametral clearance, radial clearance, clearance percentage and a simple fit classification.
This calculator compares the bolt diameter with the hole diameter to determine how much clearance exists between the bolt and the hole. It gives both diametral clearance and radial clearance.
The calculator provides:
This calculator is useful for checking bolt hole fit, clearance holes, assembly tolerance, location accuracy and whether a hole is likely to be too tight or too loose for a selected bolt.
Diametral clearance:
Radial clearance:
Clearance percentage:
Clearance margin:
| Symbol | Description | Units |
|---|---|---|
| d | Bolt diameter | mm |
| D | Hole diameter | mm |
| Cd | Diametral clearance | mm |
| Cr | Radial clearance | mm |
| Cmax | Maximum allowable diametral clearance | mm |
| Clearance Condition | Typical Interpretation |
|---|---|
| Negative clearance | Hole is smaller than bolt. Interference or no assembly clearance. |
| Very small clearance | Close fit. May require accurate alignment or reamed holes. |
| Moderate clearance | Normal clearance fit for general assembly. |
| Large clearance | Loose fit. May reduce location accuracy and increase slip before bearing. |
Enter the bolt and hole diameters, then click calculate.
| Result | Meaning |
|---|---|
| Diametral clearance | The difference between hole diameter and bolt diameter. |
| Radial clearance | The clearance on one side of the bolt if the bolt is centred in the hole. |
| Clearance percentage | The diametral clearance expressed as a percentage of bolt diameter. |
| Fit classification | A simple descriptive classification of the bolt-hole fit. |
| Clearance margin | The difference between the entered maximum allowable clearance and the calculated diametral clearance. |
This calculator checks only basic bolt-to-hole clearance. It does not replace detailed tolerance or fit selection from engineering standards.
| This Calculator Includes | This Calculator Does Not Include |
|---|---|
| Diametral clearance | ISO fit tolerance classes |
| Radial clearance | Hole position tolerance |
| Clearance percentage | Ovality or out-of-round holes |
| Simple fit classification | Coating thickness or corrosion allowance |
| Maximum clearance comparison | Structural code hole categories |
For checking bolt spacing and edge distance, use the Bolt Spacing and Edge Distance Calculator.
For checking bearing stress between bolt and plate, use the Bolt Bearing Stress Calculator.
For checking plate shear-out, use the Bolt Plate Shear Calculator.
A clearance hole is intentionally larger than the bolt diameter so that the bolt can pass through the parts during assembly. The amount of clearance affects ease of assembly, positional accuracy and possible movement before the bolt bears against the hole.
Small clearances can improve location accuracy but may require tighter manufacturing tolerances. Large clearances make assembly easier but can allow greater movement, eccentricity or impact loading before bearing occurs.
For structural joints, slotted holes, oversized holes and fitted bolts, use the relevant design standard rather than relying only on this simple clearance check.
For further fastener data, see the RoyMech reference pages: Bolt Head Clearances and Bolted Joint Design and Calculations.
For the full calculator section, see: Bolted Joint Calculators.
Bolt hole clearance is the difference between the hole diameter and the bolt diameter. It allows the bolt to pass through the hole during assembly.
Diametral clearance is calculated by subtracting bolt diameter from hole diameter:
Radial clearance is half the diametral clearance:
If the hole diameter is smaller than the bolt diameter, the bolt may not fit without force, machining, reaming or an interference fit design.
Large clearance can reduce location accuracy and may allow the joint to slip before the bolt bears against the side of the hole.
This calculator is intended for preliminary engineering and assembly checks. Final hole sizes should be selected using relevant fastener standards, tolerance requirements and design codes.