This page provides practical human-related dimensions commonly used when preparing engineering layouts and general design drawings. The information includes typical working heights, access dimensions, clearances, stairs, walkways and space requirements.
The values on this page include both general ergonomic design guidance and dimensions associated with particular building or machinery applications. Where a dimension is controlled by legislation, regulations or a current standard, the requirements applicable to the particular project and jurisdiction should always be confirmed.
For detailed anthropometric information including male and female 5th, 50th and 95th percentile dimensions, see anthropometric data and human body dimensions. For workspace and maintenance access, see human access space requirements.
Human-related dimensions are frequently required during the early stages of equipment, machinery and plant layout. Typical applications include working heights, access routes, maintenance spaces, controls, doors, platforms, stairs and walkways.
A single dimensional value should not automatically be applied to every application. The intended users, frequency and duration of access, clothing, personal protective equipment, maintenance requirements and the purpose of the access route should all be considered.
Building access requirements and permanent means of access to machinery are also different applications. For example, building stairs may be governed by national Building Regulations, while a permanent walkway forming part of machinery may fall within the scope of BS EN ISO 14122.
The following dimensions are useful general engineering layout values. They should be treated as reference dimensions rather than universal regulatory requirements.
| Dimension | Typical Reference Value | Design Note |
| Normal heel height | 26 mm | General anthropometric allowance |
| Vertical space for foot | 100 mm | General ergonomic reference |
| Stool height | 650 mm | Typical seating reference |
| Knee clearance | 660 mm | General layout reference; check intended user population |
| Table height | 700 – 740 mm | Typical fixed table/work surface range |
| Work bench height | 920 – 965 mm | Typical standing work reference; task-dependent |
| Door control / knob height | 960 mm | General reference; accessible controls may require additional consideration |
| Counter height | 1020 – 1090 mm | Typical standing counter reference; accessible counters may require lower provision |
| Instrument / control height — seated | 1070 mm | Legacy general reference; use anthropometric reach data for detailed design |
| Mirror centreline | 1550 mm | General standing-user reference; application-dependent |
| Highest convenient shelf | 1830 mm | General reference only; reach depends on user population |
For building stairs in England, Approved Document K distinguishes between private stairs, utility stairs and general-access stairs. Rise and going should therefore be selected according to the type of stair rather than using one universal value.
| Stair Type | Rise | Going |
| Private stair | 150 – 220 mm | 220 – 300 mm |
| Utility stair | 150 – 190 mm | 250 – 400 mm |
| General-access stair | 150 – 170 mm | 250 – 400 mm |
Approved Document K also uses the normal relationship:
2R + G = 550 to 700 mm
where R is the rise and G is the going. The complete requirements and exceptions in Approved Document K should be checked when designing a stair.
| Feature | Dimension | Application / Reference |
| Stair handrail height | 900 – 1000 mm | From pitch line or floor — Approved Document K |
| Stair headroom | Minimum 2000 mm | General building stair guidance — Approved Document K |
Reduced headroom provisions can apply in specific circumstances such as certain loft conversions. Refer to the current Approved Document K for the complete requirements.
Approved Document M uses the effective clear width of a door rather than simply the nominal door-leaf width. The required width depends on the direction of approach and whether the work concerns a new or existing building.
| Door / Approach | New Building | Existing Building |
| Straight-on approach | 800 mm | 750 mm |
| Right-angle approach from access route at least 1500 mm wide | 800 mm | 750 mm |
| Right-angle approach from access route at least 1200 mm wide | 825 mm | 775 mm |
| External door to building used by the general public | 1000 mm | 775 mm |
Effective clear width is measured between the relevant door stop and the obstruction on the hinge side when the door is open. Refer to Approved Document M for the precise measurement method and application requirements.
| Feature | Dimension | Reference |
| Passenger lift door effective clear width | At least 800 mm nominal | Approved Document M, buildings other than dwellings |
Lift car size, control arrangement and other accessibility requirements should also be considered; door width alone does not establish that a lift is suitable for a particular application.
For buildings other than dwellings, Approved Document M gives an unobstructed corridor or passageway width of at least 1200 mm. Where the unobstructed width is less than 1800 mm, passing places at least 1800 mm long and 1800 mm wide should be provided at reasonable intervals, for example at corridor junctions.
| Feature | Dimension |
| Minimum unobstructed corridor / passageway width | 1200 mm |
| Passing place where corridor is less than 1800 mm wide | 1800 mm wide × 1800 mm long |
For accessible design in buildings other than dwellings, Approved Document M provides different mounting zones according to the type of control.
| Control Type | Height Above Floor |
| Socket outlets, telephone points and TV sockets | 400 – 1000 mm |
| Switches for permanently wired appliances | 400 – 1200 mm |
| Controls requiring precise hand movements | 750 – 1200 mm |
| Simple push-button controls requiring limited dexterity | Maximum 1200 mm |
The appropriate requirement depends on the type and purpose of the control. These building-accessibility dimensions should not be confused with machine-control positioning, which should also consider operator reach, posture and the task being performed.
Permanent working platforms and walkways forming part of machinery require different consideration from building corridors and access routes. BS EN ISO 14122-2 provides guidance for permanent means of access to machinery.
| Machinery Access Feature | Dimension | Design Note |
| Normal clear walkway width | At least 800 mm | BS EN ISO 14122-2 |
| Walkway used by several people simultaneously | At least 1000 mm | BS EN ISO 14122-2 |
| Occasional-use walkway under permitted restricted conditions | May reduce to 600 mm | Subject to the conditions and risk assessment specified by BS EN ISO 14122-2 |
| Normal head height over machinery walkway / working platform | At least 2100 mm | BS EN ISO 14122-2 |
| Local obstruction at head height | Not less than 1900 mm | Restricted condition requiring appropriate protective measures |
The width required for a machinery access route should also consider the task, frequency and duration of use, tools and components being carried, protective clothing, the number of operators and the need to evacuate an injured person.
For fixed ladders within the scope of BS EN ISO 14122-4, the spacing between successive normal rungs should be constant and between 225 mm and 300 mm, subject to the additional requirements of the standard.
For panic exit devices within the scope of BS EN 1125, the horizontal bar is normally installed between 900 mm and 1100 mm above finished floor level. The manufacturer's installation instructions and applicable fire-safety requirements should also be followed.
The following original RoyMech illustration provides useful visual guidance on human space and stair requirements. The dimensions shown in older illustrations should be checked against the current requirements applicable to the project before being used for detailed design.
The dimensions above should not be confused with population-based anthropometric data. Where equipment is designed around the physical dimensions of operators, suitable percentile data should be selected for the intended user population.
RoyMech provides male and female 5th, 50th and 95th percentile data for height, eye and shoulder position, seated dimensions, hand and foot size, body breadth and reach on the Anthropometric Data and Human Body Dimensions page.
Designing for the average person is rarely sufficient. Smaller users may govern reach requirements, while larger users may govern clearance and access requirements.
Human-related dimensions should be selected according to the function being designed. Normal operation, inspection, maintenance, component removal and emergency access may each require different space.
Frequency and duration are important engineering considerations. A location used continuously or repeatedly during a working shift may require different ergonomic provision from an access point used only occasionally. However, infrequent use does not automatically justify reducing a mandatory safety or access requirement.
Clothing, footwear, gloves, helmets, respirators and other personal protective equipment can increase the required working envelope and may reduce reach, mobility or dexterity.
Human-factors guidance should be considered alongside safety, security, maintainability and operational requirements. Mandatory requirements should be distinguished from recommendations and general ergonomic guidance, and the applicable regulations and standards should be confirmed for the particular application and jurisdiction.